Sick of Feeling Sick

I just really...have not been feeling "normal" for these past few weeks. It really seems like I can't catch a break between trying to keep my grades up and being focused on worrying about every little shitty thing in my life. I hate to be so overly negative, but it's hard to even think of positive events with my current state of mind. I feel like I've lost myself. Ever since I decided I was giving up on vet school (and I haven't really told that many people yet...), I kinda have been feeling like the world is crashing down on top of me. I'm no longer certain where I'm going with my life. It's like...I know what I want to do. The things that hold me back from doing these things  are actually very concrete things. Just to name a few:
1.) I couldn't change my major at this point, even if I really want to.
2.) Every different thing I consider has some different pre-req for grad school that I'm not going to be able to do because I'm already almost at my 150 credit limit (also related to #1)
3.) I also feel like I'm not involved in enough, even though I kinda did bust my ass when I was doing all this stuff for Pre-Vet Club. I have a lot of volunteer hours, but they're all pretty much specifically related to animals. I'm not sure how well that's gonna look on me in the long run.
4.) Money
5.) Confidence*** I'm not confident in my abilities at all. I always feel like everyone is doing better than me, and that's always been a huge problem for me mentally.

Now I just always have this sense of sadness I can't shake. I still go out and do fun things every once in a while, but even when I'm laughing and goofing off with my friends, I'm still overwhelmed by crazy thoughts and worries. Then it gets to the point where I just want to go lie down by myself somewhere and cry; let it aaaaall out. It makes me feel so trapped...I just want to be normal. I don't even know what "normal" people think about, but I'm pretty sure it's not the same as what I think about - obsessing over the thought of one thing or one person over and over and over.

Laaaawd, please give me strength as I continue to {try} to work out the kinks.