OP, I'm in the same school system variant as you; I'm a senior, AP student, and National Merit they-haven't-told-me-if-I'm-a-Finalist-yet.

First off:
DROP AP BIO RIGHT NOW.
RIGHT NOW RIGHT NOW.
There is no reason for a sophomore to be in a second-year science course. Wait until your junior or senior year for that. I took AP Chem my junior year and I dropped it after the first semester because it was eating up so much of my time. I haven't looked back since and I laugh at my friends who have to stay at school doing labs two hours a week after school.

Also- I'm not sure why you're in two math courses right now. I took Algebra I in 8th grade, Geometry in 9th, and Algebra II in 10th. I'd drop whichever is the harder class for you right now. It seems like Algebra II is giving you more trouble right now, which, like >>4 said, shouldn't be the case.... I slept through the second semester of that class. If you're trying to catch up so you can take calculus or something senior year, then consider taking it through either a local community college or an online/correspondence course that your school will recognize. The way my school works, outside classes count for credits towards graduation, but the grades don't factor into the GPAs, so that should take some stress off, since you just have to pass.

As far as de-stressing yourself, figure out something to do that will help you calm down. You don't have to go the weed route unless you're of >>4 and his ilk, but find whatever it is that helps you. For me, repetitive hand movements calm me down, like knitting and origami and somesuch. Writing in a diary/journal/etc. may help too, since you can sort through your thoughts that way.

Good luck OP. Don't worry about things too much; enjoy your high school years while you have them. I'm still somewhat in shock that my senior year is halfway over, so don't take your time for granted.