I originally had a lumpectomy with clear margins. I have dense breasts which makes detection difficult, so a few months later I decided to have bilateral mastectomies. The surgeon did not think I needed to have a mastectomy at all but I am a bit of a worrier and decided to do it anyway. Having a mastectomy does not still prevent any possible metastasis. I am a few years older than you and not having boobs does not matter to me, I just wear prosthetics when going out. Having a mastectomy/mastectomies is a very individual decision with no right or wrong answers so think about yourself. I did not have radiation but I had chemo as my BC was HER2 positive.
Good luck with your treatment.