Ok, I'm 13 years old and used to be overweight and am trying to be more healthy. Throughout last year (2009), I've been going to my school's weight room and trying to eat healthier. Im 5'7 and weigh 163 pounds. I used to weigh about 150 in the summer. When I'm at my weightroom my routine usually consists of about 15-20 curlups with a barbell, 50 bicep reps with 10 pound dumbells (I can do 15 but my guidance counselor told me to stick to 10 because it's better to not over-strain my muscles.) I've been doing the eccentric pose with a 10 pound weight for about 10 times. Jogging a mile and a 500 meter rowing simulation. I've also been doing leg exercises. Sometimes when I exercise I think I way over-exert myself because sometimes after doing a mile hard I would feel like vomiting and when I tried to sprint 1 mile on a treadmill I almost vomited. The problem is I don't know when enough is enough, like I don't feel like vomiting until I actually stop or when it actually is about to happen. Is it normal to get near the point of vomiting and dry heaves or should I consult my doctor? Is that 13 pound weight gain normal or is that muscle? I'm sort of intrested in yoga as well, does yoga train your core?