Do masturbation causes infertility and sexually transmitted diseases?

Hi doctor,

When I was a kid, I used to masturbate, sometimes alone and sometimes with my cousins or friends when we used to do sexual activities. I started this at around 13 years of age. I knew it was terrible; I just never knew how bad. I always kept it from my parents. I am now getting bad thoughts about it, like what if I can get infertility and I cannot have a baby, or I could get a sexually transmitted disease? Me and my cousin used to have sex when we were around five years of age. Will this childhood memory affect me in the future?

Thanks.