Hi I face a problem of erectile disfunction as whenever I am about to have sex after the foreplay I don't know my penis loosens up and I am not able to have sex. I don't know if I get nervous or what turns me off but I am not able to maintain an erection hard enough when it comes to sex. Everything is fine during the foreplay but the problem occurs when having sex. So I guess Viagra might help me to maintain an erection good enough for sex. I have not taken Viagra before and want to know the recommended dose.