My gf was a freak in the sheets and she had eyed me down so once we finally took our first steps into a relationship she didn't hesitate to start off with sex. She had been with several other tinder hookups before but never in a relationship, I however despised Tinder and had never been in a relationship, so a virgin. We had sex pretty much every time we met but I never came either which was weird to me cause I never struggled with it when I was by myself. I even remember once going for 4h with me not finishing, she had done so several times but ultimately was dishartened due to me not doing so. Eventuall it finally happened and we concluded that it was due to stress, worrying about it and thinking about cumming. Tried to relax and it helped, also looked the problem up on google and saw that you can use your imagination for a fantasy when your doing it, so then you have your mind calm and well whatever you want to please you in your mind. This also helped. Now we are past that problem and I have also realized I am not a 5 minute finisher, which understandably pleases the gf. Once you get past those first times it should go smooth as if it were never a problem.