Something is wrong with my penis. Help!

Something is wrong with my male reproductive organ. Before 7-8 days , after I masturbated, my penis went limp and my testicles shrunk. I am having trouble getting erections or having very weak erections. So I just quit the habit for some 3-4 days, but not much improvement I could see. I tried masturbating yesterday, it got erect alright and then I reached orgasm but there was almost very less or no semen ejaculation. Today I also tried, i have my erection back, I reached orgasm state but there is very less or almost negligible semen discharge. Normally before , if I didn't masturbate for 3-4 days, and then attempt masturbation I would get huge semen discharge. I don't know why my penis is behaving in such strange manner. Please help