taking on too much responsibility

Okay, SO I know this is not really a work question, but its the only place it fits. I am finding recently, as a student, that I have been taking on way more than my share of duties. I am in five classes, have a part time job, in the band, Orchestra, and a semi-professional brass ensemble. I am also the secretary of the French Club (but everyone treats me like the president because she is super-loopy).

The thing is, I am just soo tired and frustrated. I hardly have a minute for myself. And when I do take a minute, I am usually neglecting some other duty. The other day I got screamed at by one of the French Exchange Students because I told her I'd be somewhere and I wasn't there. She had no right to yell at me like that even if I was in the wrong. I feel like I have set myself up for this because I tell people they can count on me, and usually they can. But people start to take advantage.

For example, I was the group leader in my Bio Lab group and we were doing a project on Modern Feline Problems. I volunteered to put together the reference list, which is no small task when working with obscure sources as we have been. I asked the group to send me their references two weeks ago and nobody did until yesterday (when the project was due). So I had to explain to the prof why it would be late. And one girl still didnt send me all the right info. Finally I had had enough and I sent on what I had for references to the prof and told the girl it was up to her to get her portion in.

But here's the thing. I know I take on too much. And I know I need to stop (its causing health problems: chronic back problems, anxiety disorder, sleep deprivation, I constantly have a cold). But I don't know how to say no to things. I want to do everything. And it hurts me when I cant be there for people, when I can't be reliable. Part of it is that I like the things I do when I have time for them. Music is a big part of my life, and I cant imagine giving any of my groups up. And I like French Club because it is an opportunity to visit interesting places like Quebec and Montreal. I need my job because I am broke, and classes are obviously important.

I mean, I maintain straight A's, and I am involved in all these things. For a while I was proud of all I could hand, but now I am just tired, and wishing I could go to a party or the movies once in a while like the rest of the college people!

Help me!