If Chem and Bio at the same time are too much for you, perhaps medical school would be too much, too, and you might be better suited for a different career path. Work hard in both and see how it goes.
If you work well in a group, form a study group of like-minded students in your class and work together reviewing homework or doing problems beyond what is assigned or explaining difficult concepts to one another. Draw a bright line between group work and assignments that are handed in. Under no circumstances should you collaborate on homework or lab reports, lend lab reports or homework to others or touch another student's clicker. Never cut and paste from one source into something you will hand in as your own work. Do not cheat, ever, as this is a death sentence in medical admissions.
If you hit a snag, seek help right away. Some schools offer tutors, office hours, or TAs who can help with concepts you have trouble with.
If this is your first term, spend it getting to know people and getting to know what the school offers. Find something fun that gives you a chance to blow off steam. If you enjoy sports, join an intramural team. If you enjoy performing arts, get involved with a performance group. If you like journalism, activism or environmentalism, there is likely to be a group for that on your campus. You can't and shouldn't figure on studying 24/7 and you should find something enjoyable to do with some of your spare time. If you must work, or if you have been tapped for work-study, find a job that gives you the opportunity to work with the public or as part of a team. My kid works at a coffee bar on campus. By this time next year you should have two, or at the most three, things you really love that take some of your free time. These might be school based activities, community-based activities, or things you do on your own (hobbies like repairing electronics or making jewelry).
If you must drink, limit yourself to no more than one drink. If you can't limit yourself to one, don't drink. If you want to avoid having to report being in trouble for alcohol, don't drink until you are 21, avoid locations where underage drinking is taking place (even after you turn 21) and do not store alcohol in your university-controlled living space or allow others to do so.
You won't take the MCAT until sometime after your second year of college. Traditionally, it is taken in April of junior year but that has changed with the increased flexibility that students have in scheduling the exam. You should figure on 8-15 weeks of solid preparation for the MCAT but the earliest you should take it is about 2-2.5 years from now so relax for the time being.
