Its my first year of college, and my past senior year/summer was hell on earth. Two good relationships ended for no good reason. Intense friend fights. I was very sick for several months, and kept getting sick afterwards. I wasn't challenged mentally, so I started giving up in school, it didn't seem worth it. My grandmother is in a very poor state, and we almost lost her. Ive had bad insomnia. I had many months worth of panic attacks, and some stupid friend almost got me arrested (it wasn't a big deal, I'm not a bad kid) I've been ridiculously stressed, and I've lost my appetite. All my classes were dropped and I had to spend days salvaging my schedule. And my dad and I have a bad relationship, which translates into my sister and I having a bad relationship (and she's only 10). I feel like an awful person for not getting along with her. Ive had a short temper with everything and I'm never happy anymore. I just don't know what to do. Help?

I'm going through something similar in terms of mood. Very different situation and I'm a lot older though.
I have no great words of wisdom. When enough events 'conspire' to tip the balance between coping and flying off the handle or feeling totally overwhelmed, all you can do is list all that is going wrong, drop the lesser ones from your mind, and solve what you can. Not easy, of course. The one incident - drop it. The two friends - write them letters (on paper) saying you miss them. Grandma: tell her you love her. Little sis: ditto, and keep dad out of the relationship (don't even talk about him with her). Dad: ask to sit down and talk.
It's possible that stress made you sick but it's also possible that illness is causing insomnia and stress. Care to mention what it was, and are you sure it was correctly diagnosed (if it was)?