right side of ribs..

For the past month I've been having very sharp pains underneath my ribs on the right side, about where my stomach is, nearly every time I exert myself (even slightly).  It started as a stich one night when I went out dancing with friends, but it just won't go away.  I'm a reasonably healthy, 20 year old girl.... I don't feel like I should be having a problem like this.  I did some research about ulcers, and I read that I may be at an increased risk for them because I have type O blood, I tend to skip meals and eat unhealthy food (due to a busy/weird schedule.. but nonetheless), I only recently quit smoking, and I am pretty stressed (again because of the busy/weird schedule).  Before researching ulcers, that's what I thought I have just because of how stressed out I am all the time.  But I don't get any pains when I eat, the pains don't wake me up in the middle of the night, I don't have black stools, and I haven't felt the need to vomit because of the pain.  I work out as often as I can, but a pain like this never occured before that night at the club.  It feels exactly like when you get a stich from running for too long.  I've tried to do extra abdominal exercises to help fix the problem, but that only makes it worse.  Any ideas??

Thanks!!