3.8+ in college is definitely very doable. One major factor is motivation. For most college classes, attendance is optional and homework is not graded. For some students, "life" starts to happen and they end up skipping lectures and homework assignments. Then when finals roll around, they're 3 lectures behind and haven't had much practice solving the types of problems that are going to be on the final. If you show up, stay engaged during lecture, do the work, and try your best to treat "optional" as "mandatory" (within reason, there will be times when the professor assigns way too much), that already puts you ahead of many people in the class.
Also, in high school, you're locked into taking pretty much the same classes as everyone else. In college, you've got some freedom to focus down on the area that interests you/the area you have the potential of doing well in. If your strength is in literature, that doesn't help much because you still have to take and excel in foundational math/science classes to get into med school. On the other hand, if your strength is chemistry and your biggest weakness is the arts, you that freedom will help you tremendously since you'll be able to mostly, though not completely, avoid the arts classes that would be really tough for you.
With regards to med school admission: In medicine, just like in anything else, there's a wide range of possibilities, some of which are more desirable than others. There are absolute rock stars out there with 4.o GPA's from competitive undergraduate institutions that end up going to top-ranked MD schools in popular cities like Boston or New York, matching into competitive resident programs (which is the next step after medical school, the one which determines your specialty), and taking on very desirable posts like faculty positions at Johns Hopkins or private practice dermatology in Beverly Hills. Along the same lines, there are people with GPAs less than 3.5 and mediocre MCAT scores who end up going to DO schools (more on that later) in "undesirable" rural locations, and have more limited options as far as what to specialize in after med school. In short, you don't need perfect grades to become a doctor. However, if you're a a weaker applicant, you may end up taking a hit as far as location, prestige, and job prospects.
With regards to MD vs DO: Essentially, there are two different organizations that credential medical schools. Schools credentialed by the AAMC grant the MD degree, and schools credentialed by the AOA grant the DO degree. The MD degree is far more common. DOs are able to do some things that MDs are not (osteopathic manipulative medicine) but only like 10% of DOs actually end up using those skills in practice, so it's not really a meaningful difference for your career. There are residency programs that accept DO applicants, but not MD applicants. On paper, all residencies that accept MDs are also open to DOs. In practice, however the most competitive MD residencies will strongly favor MD applicants over DO applicants. On average, DO schools do accept students with slightly lower GPAs and MCAT scores than MD schools. For someone who wants to do primary care, either the MD and DO degree would serve them well. For someone who wants to specialize in a competitive field like orthopedics, neurosurgery, or dermatology, an MD would definitely be better. For anesthesiology in particular, I'd say the MD would be an advantage, but either would do.
You are ready yet to tackle those MCAT physics question but you will be! May be after freshman year of college, you will figure out that you really enjoy Physics and become a Physics professor in future 
