i have nothing abnormal about getting an erection and ejaculating once. but after i do that and get another erection within a period of 8-12 hours the second erection is uncomfortable/borderline painful and although sexual activity still feels good then its not as good as the first. i'm 19 and its been like this as long as i can remember. is that normal? a third time is fairly painful. is that normal? should i see a doctor and if so what kind of doctor?