I am 22 years old and I have no trouble getting an erection during masturbation or foreplay. I can get really hard. However during sex I cannot maintain a really hard erection as I do during foreplay and masturbation. At some point I feel getting softer. Also sex does not feel very stimulating to my penis. I feel that I would never reach an orgasm no matter how long I continue. Partner seems to be enjoying it though. And if I attempt to stop, to change position or because penis was accidentally removed my erection is easily lost and without removing the condom it is hard to get it back. I am really confused cause I know there is nothing wrong with me physically and mentally. I am a relaxed type of guy. No worries. I enjoy my life. I do not understand this. Any advice and help is welcomed.