I am a 23 years old male. Last week I had sex with her. During first round I first made her reach climax with fellatio and upon intercourse I came too quickly - say within 10 seconds. After 25-30 minutes we went for the second round. This time without fellatio (oral sex) we directly got engaged in intercourse. And This time I lasted longer - say 10-15 mins. She again reached climax as I could see the sticky fluid coming out of her vulva and could feel the contraction around my penis. But I couldn't ejaculate and reach the climax and suddenly lost my erection. But this didn't happened before I was able to ejaculate and reach climax during the second time too. Any suggestion or medicines or treatment?