Sharp pain at lower right ribcage during exercise? 10 Points best answer?

Ok so Im trying to lose a few pounds because as a high school runner I should be on the thin side, I do 2 full elliptical workouts every day at level 20(max) and each workout is an hour, I usually burn 2000 calories a day and also take a fat burner to help just one a day though, During the middle of the first workout a sharp pain in my right lower ribcage was strong with pressure only for a few seconds. I was not sure if it was the stimulant or over-training, I'm still healthy but I just work out allot to lose weight I'm a 16 yr old male height 6'1 weight 174 and just one pill(Roxy lean) can't be enough to give me heart palpitations.