Is "dry" masturbating bad for my prostate?

So as a teenager in a pretty religious house fapping was frowned upon. Being a teenage boy that was not really going to stop me, I just had to be discrete. I was able to figure out a way to make hiding it easier though. When I was ready to cum I just put a lot of pressure on the bottom of my penis at the base, not on the vein mind you but the soft part on the bottom. This would allow all the good feelings but then nothing came out so no mess to clean up. It never hurt and I never noticed any repercussions. I did it often as a teenager and still do occasionally in bed if I don't feel like getting a sock or something. The main concern is that with all the talk of fapping on here no one has ever mentioned this method that I am aware. Is this bad for me and if not, where does the semen go if not out?

Thanks,