Less developed smal testicle both testis

My both testis is small and less developed however I have no any issue with it like pain or one big second small neither it's a new problem. The problem is my testis could develope smaller than a usual testis, it was never big as it developed. I had it small since my childhood and for the size I did not get any diagnosis yet. I think my testis size is 3.5 centimeter it it looks like a 12-14 years old boy and my penis size is 5.5 inch when erect. Without erection it's look very small sometime like 2 inch and sometime like 3 inch and my ejaculation time is 10-20 second when full in mood and my erection is not too tight as it should be. My history is masturbation since childhood with friction of my penis in bed without having an erection to get an orgasm.