I am so sick of making bad grades help?!?

I hate my academic life. I take 4 AP cles, and its right before midterms now and I'll probably have a C in three of them and a B in the other. And I take 2 honors cles and will probably get C's in those. I got all As and Bs last year in honors cles and thought I would this year too but it's just not happening. I try to stay awake late at night and get my work done but I guess I am just too effing lazy. And I have dance 4 nights a week so I don't have the effing time and I can't seem to stop wasting it doing stupid stuff on facebook and youtube. I am really mad at myself for letting this happen and I'm so sick of seeing other people do better than me on ignments and I just never seem to get up to their level. I pay attention in cl but sometimes I still don't understand the stuff we do. I know that I could get better grades but I just don't know how and don't know what I am doing wrong. I just can't motivate myself to work and hate how all my teachers give me that look like I am stupid and lazy. I just want to prove them wrong. I really do want to do better but I don't know how, I try everything but it doesn't work. I have one semester left of this year and I desperately want to improve my grades but how do I do it? Any straight-A students out there that can help?