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)
40(f) - 130lbs - 5ft 7. I have always focused on my flaws, what I would rather have or how I would prefer to look. over the last year or 2 I've realised I should be grateful for what I have.