Please advise on semen discharge

I am 30 year old male and have trouble maintaining erection. I also have semen discharge after urinating and when attempting to have sex. I don't think it's an STD but problem started after splitting up with last girlfriend about 3 months ago. Have not been able to have complete sex with new girlfriend as erection fails followed by discharge of semen. She thinks it's connected to fact I drink and smoke heavily. Any ideas?