when I sexually excited, then some liquid comes out, at that moment I have to urinate, after urination I feel pain below the back. My erection is not last long time and when I masturbate 7 days after, my semen volume is low and I think my sperm concentration is also. When I was going to mate with my girlfriend my penis is not erected fully. Whenever I feel my penis is erected, then I have to urinate. What will I do now....