Why am I having mood swings?

[Kyle]

I'm a 22 year old male. My 24 year old sister's car has broken down and for the past 4 weeks I've been dealing with taking her kids to school, my own classes, and driving her places. I love her to death so thats not a problem. I enjoy the time with her because I came close to losing her last year and I try to spend as much time with her as possible. Well, since her car broke down... I've been getting very little sleep. I've been super stressed with college, and life in general. Lately, it seems like small things can set me off. I can be okay then someone makes a comment and I take it the wrong way or blow it way out of proportion and then I'm angry or depressed most of the day. I cant seem to take jokes at all now, and I've also had trouble controlling my anger. For example, I had a bad day at school, came home and through my cell phone. Luckily my sister fixed it. She told today that I acted "bi-polar". She really knows me and she is with me a lot so she wouldnt say something like that for the heck of it. I dont want to be crazy, it just seems like lately I've been emotionally drained and cant deal with the emotions. I'm worried that I might have something and I dont have the money to pay for counsling, not that I want that anyways. I've always thought I could control my emotions myself and having a mother who was skitzophrenic makes me feel like I could become like her someday. I just dont know what I'm going through but I hate how Sat (I was fine) and today I was a emotional wreck for the better part of the day.