i am 18 and i used to masterbate like everyday since i was like 13 i have stopped but now i try to have sex with my girlfriend and i can not keep an erection when we are about to do it and then she will get me hard and i will ejaculate pretty soon. did masterbation do this to me and is there any way i can be hard as a rock for a long time so i can give my girlfriend a great orgasim.