First of all, is it absolutely true that you aren't smart enough, that you don't have what it takes? Can you be sure of that? No, you can't, yet. Relax, I think the jury is still out. At this point, the alternative, that you are smart enough and have what it takes, is just as true.
Be gentle with yourself. If it helps any, similar thoughts crossed my mind at your stage in the process. I also went back to school to retake my pre-requisites, close to 10 years after I completed my initial degree. I also felt slower, at first, than the students around me. The thing is, when you are away for a while, you are out of practice with academic work. Your son and most of the students you are in class with have been studying continuously, so they are in the thick of things. If you haven't done something in a while, understand that it may take some time to get back into the groove. Give yourself a break and allow that transition to take place.
How are you studying? Are you doing it efficiently? I find that if you haven't studied in a while, you may be doing it inefficiently. Some of it has to do with focus. Are you 100% there, concentrating on the tasks at hand, or are you interrupting yourself with other thoughts or tasks? One of the keys to rapid studying, is to be 100% there, or as close to it as you can. Set up the environment so that you can do that.
Another key to effective studying is to chunk the material. Break it up into easier bites. It's really hard to remember a long string, like "qwertyuiopasdfghjkl." However, if you break it up into four bites such as "qwerty," "uiop," "asdf," and "ghjkl," it's quite a bit easier to recall. Consider doing that with your study material.
Another key is to translate complex concepts into your own words, using analogies you are already familiar with. If you can do that, you will understand the material faster and remember it better. Create examples that make sense to you. It works better when you can turn concepts into examples and then translate that back into the concept: con-ex-con.
Another key is to focus on high-yield elements and blow through the less important ones. Learn to triage what is critical and important and spend your time accordingly. This is very important when you have limited time and when the information is flowing at you hard and fast and very volumous. Of all things, this is probably one of the most important skills in medicine. For example, how would you process the following:
An 87 y/o obese male with a PMH significant for CHF, HTN, Dementia, and DM2, presents to your office c/o increasing dyspnea, particularly on exertion and lying down flat, pedal edema, fatigue, and non-productive cough, worsening over the last 3 days. He denies any chest pain, N/V, fever, chills, or abdominal pain. He states that he "went out with the boys," and ate a large, salty pizza and had a couple of 12 oz beers prior to onset of symptoms, but thinks he might be coming down with the "flu," since everyone at this house is sick and he has been having a lot of nasal congestion lately. He is alert and oriented x 3, and mentating well. Your physical exam is significant for bibasilar rales, a 2/6 systolic murmur, and 2+ pedal edema. His meds include Toprol XL, Norvasc, Metformin, Amaryl, Aspirin, Lisinopril, Hydrochlorothiazide, and Colace. His vitals are BP 130/80, Pulse 100, 20 breaths per minute, and SpO2 88% on room air. You get a set of labs and find that his Hgb/HCT is 12/40, WBC's 8, Sodium 135, Potassium 3.5, Bicarb 25, and glucose 120. His BNP is 3000. His EKG is normal, except for mild tachycardia, LVH and bilateral atrial abnormalities. Cardiac enzymes are negative. A chest x-ray shows blunting of the costophrenic angles, cardiomegaly, and Kerley-B lines.
Long passage, right? That patient is presenting with acute exacerbation of his heart failure, likely secondary to dietary indiscretion. What are the key facts here? Let me highlight them in bold:
An 87 y/o obese male with a PMH significant for CHF, HTN, Dementia, and DM2, presents to your office c/o increasing dyspnea, particularly on exertion and lying down flat, pedal edema, fatigue, and non-productive cough, worsening over the last 3 days. He denies any chest pain, N/V, fever, chills, or abdominal pain. He states that he "went out with the boys," and ate a large, salty pizza and had a couple of 12 oz beers prior to onset of symptoms, but thinks he might be coming down with the "flu," since everyone at this house is sick and he has been having a lot of nasal congestion lately. He is alert and oriented x 3, and mentating well. Your physical exam is significant for bibasilar rales, a 2/6 systolic murmur, and 2+ pedal edema. His meds include Toprol XL, Norvasc, Metformin, Amaryl, Aspirin, Lisinopril, Hydrochlorothiazide, and Colace. His vitals are BP 130/80, Pulse 100, 20 breaths per minute, and SpO2 88% on room air. You get a set of labs and find that his Hgb/HCT is 12/40, WBC's 8, Sodium 135, Potassium 3.5, Bicarb 25, and glucose 120. His BNP is 3000. His EKG is normal, except for mild tachycardia, LVH and bilateral atrial abnormalities. Cardiac enzymes are negative. A chest x-ray shows blunting of the costophrenic angles, cardiomegaly, and Kerley-B lines.
I don't expect you to know the medicine or to recognize the important elements here, but see how I scanned the long passage? That's key to quickly assessing what you need. You need to train yourself to do that.
Another key to effective studying is to review vital information at least three times before an exam. Studies show that this helps solidify the material in your memory. Don't dwell or lock onto something unnecessarily if you already know it, unless you don't understand it, in which case you will want to supplement with other material to increase understanding. I've also found it useful to approach complex information thusly: when you first come across information, skim it quickly to get the gist, then review it more deeply, highlighting the important elements. Then review the important elements a few times.
Taking tests. How are you taking your tests? Are you an efficient test taker? Analyze how you are proceeding. In taking tests, I have found it best to scan the test quickly to triage the questions in terms of difficulty. I will attempt to answer the easier ones first, followed by the intermediate and then the difficult ones that require more thinking. If I don't know the answer at first, I will try to eliminate the wrong choices, so I can make a guess. If I'm still not sure, I will mark a preliminary answer and move on. You don't want to dwell or obsess over any one question, provided they are all worth the same. If you find yourself taking too much time on one question, just mark a preliminary answer and move on. Come back to the ones you aren't sure about if you have time. Mark your answers in blocks in the answer sheet. When reading questions, read for the key facts. This increases speed.
Practice a lot. Do a lot of practice questions. After a while, you will begin to see the patterns and learn how to make educated guesses faster. The key to fast test taking is ultimately in the practice.
Take what I offer here with a grain of salt. It may not be accurate and it may not work for you. Just offering some suggestions.