I'm 5'10 at 17. i'm also 13 weeks pregnant and my weight is about 225. this lady said i can only gain 7 more pounds throughout my pregnancy. possible?

In theory, yes, but: Check with the Ob-Gyn to see if such ideas are good or bad. If a woman is 225 lb. with no baby, and wants to be 232 at the end of pregnancy, she would have to use up a lot of stored fat. Theoretically, 232 minus 7 lb. for baby, 2 for placenta, 5 for uterus+breasts, 5 for extra blood, and 5 for extra water, comes out to 208... which suggests using up 17 lb of stored fat from before the pregnancy.