It took me until my 50s to stop being self-conscious about my slender body and skinny arms. Exercising more helped a bit but it was mostly in my head. My advice - love yourself now! (The sign was for a Twitter pro-nudity campaign)
F20 - 84 pounds - 5β2 (Yes I know what you are probably thinking and yes Iβm getting help for my issues. I posted this for body positivity for myself because Iβm slowly gaining weight and learning to love my self).