Breast and body insecurities...

I am not a big perso i weigh maybe 100 lbs and have insecuriies about my body and its size... I lost my v card at 15 and will not take off all my clothes during sex because my size makes me feel like theres a high possibility of me and my man breaking up and him telling people bad things about me idk why i have no real real reason compared to some people i wear a 36b-c depends and a size 1 in girls but idk can someone help me... Advice needed