This is college. Just cause you got into college doesn't necessarily mean it's meant for you. That being said, it is easy to be overwhelmed, but get used to it and suck it up. If you aren't staying up till 4 a.m. every night studying then you aren't studying enough IMO. Every course is doable, people graduate with 4.0's and some of those people are biochem majors. No excuses, we were all freshman at one point and we all plan on getting into medical school some day. You should know that your teachers expect a certain level of effort into the classes you take (obviously a chem class requires more effort than a humanity and what not) and you as a college student have a duty to give that effort. Your grade will reflect how hard you study, there is nothing that a professor can teach you that you cannot learn yourself in a book. Get used to going over notes, reading through the textbook before the lecture so that the lecture is like review. If you stay on top of things you should never get overwhelmed. Study as much as you can and party like a rockstar on the weekends. Your gpa is all up to you. If you can't handle it, stop complaining and call it quits.
P.S. You can have a backup career in any major and still get ur pre-med requisites done.