i always get hard erection to perform sex when i am alone or watching porn, i do masturbate always whenever i want, i do have solid erection and perfect sexual intercourse when i meet any prostitute, but now i have a girlfriend and each time we are together to have sex it will seems as if my penis is not getting very harder, i finds it very difficult to penetrate her, my penis do not get harder any more to penetrate her, but if she went away i will regain harder erection, i feel ashamed and sometimes she says that i am not a man. what should i do?