My jaw is huge please help.?

Growing up my face was fine loved my jaw shape really thin face ect.. I gained a lot of weight during the last year and a half got depressed but took control and lost the weight but here's the problem since I lost the weight my face looks 30 years old its horrible I'm 18 by the way. I just looked so diffrent I came to realize my jaw muscle got HUGE not big HUGE to the point my cheeks are pushed out and without even biteing down my jaw is really hard its the top and bottom jaw muscles on each side. It stretched my skin out its just horrible I look so weird. What can I do to get these muscles to go away in my face it even hurts when opening my mouth up wide to yawn. I need these muscles gone Idc what it takes I miss my thin face. Also I was told when I gained weight my jaw muscles grew from eating so much. Even wheb I eat hard food such as a long roll or beef jerky my face blows up and the muscles are extra hard and pop out.