You need to take ONE step a time. You are not a super human and cannot do EVERYTHING perfect at the same time.
I'm always second guessing my treatments.
Choose the treatment you are confident/ most confident about. Always start easy and slowly - in this case you will most likely have time to stop before hurting a patient. Do not expect results for the next 1-2 weeks. (Good if there are results, but many conditions take months to improve.)
worrying that my patients won't improve.
If possible, throw this thought out of your head and berry it forever. No PT can guarantee their patients that they will definitely improve. There are tooooooo many factors far beyond your power that affect patients progress (their medical condition, compliance, their work, family, financial situation, mood, etc, etc). You are offering your patients treatment which you believe may (but not must) improve their condition. You and your patient are trying those treatments and see if they help the patient or not. If they do, great. If they do not, you offer another treatment you believe MAY help. If you have tried treatments that you believed might work and none of them did, you refer the patient to another healthcare provider you believe may be able to help the patient. Feel free to ask an advice from you CI and co-workers. If everyone is completely clueless what to do, refer the patient back to his PCP.
stressing over improving my documentation speed.
Pay attention to this only if you are not passing your clinicals because of slow documentation speed. If it is not an issue for your CI, then you do not need to worry abut it. During clinicals, I had to sacrifice my free time to complete documentation (stayed in the clinic extra 60-90 min sometimes to finish paperwork). When you start working, you will not have to do that (unless you choose to) since it is illegal for your employer to make you work off the clock for free.
I'm not sleeping or able to eat in the morning due to worry.
Try to realize that not sleeping and not eating will not benefit you or your patients in any way. If you sleep better and eat better, your brain will function better, you will be able to make better decisions in the clinic, you will have better communication with your patients, and most importantly you will have your sanity that your patients will need you to have.
I am reaching out to my primary care provider about this
Good idea! S/he may know you better and may be able to give you more specific advice/strategies how to cope with your anxiety.
Good luck and just for now, make your goal to pass your clinicals and nothing beyond that. Right now, your CI is responsible for all your patients, not you, you ARE IN TRAINING. So if you are not able to provide patients with the best care, CI will compensate for that (that's what they are for!). Do put yourself first PLEASE.