I feel fat?

I am 14 ,5'3 , and 120 lbs. My friends tell me I am skinny but I feel a bit chubby. Like I always look in the mirror and see Im getting fat. I want to be fit like kind of abs but I can't seem to actually workout. I don-t eat so healthy but not so bad. Am I fat? Or am I just crazy haha. And how do I get into working out. Also I would love to eun but I have asthma and it sucks and although that isn't an excuse it's still a problem. Help!