While I get it that you feel that you ejaculate pretty fast, it might help if you take the focus off of you. We are men, we all ejaculate and it's going to take time for our bodies to adjust. But I think if you made your primary concern with giving her pleasure (whispering in her ear or nibbling on it, playing with her hair, using your other senses like smelling her hair or the smell of the soap on her neck and body, even oral sex if that's something you already know she will enjoy), you will take the focus off your ejaculating too early. And for goodness sake, so what if you still ejaculate. It happens. Don't bring any extra attention to it as if something is wrong with you. That's the difference between being a boy and being a men. It's how graceful you deal with unexpected setbacks. A man focusing on giving her pleasure won't think about his ego and would leave the pride at the door. Try lots of different types of foreplay; call her throughout the day to get her juices flowing and build up to intercourse. Something that I find that works is without even touching her breast, vagina, or buttocks,
slowly rub your hands all over her legs, back, shoulders, neck, lips, etc. The roughness of our male hands on their soft skin drives them crazy. Get rid of the pride and ego, and stop stressing over the possibility that you might orgasm, I promise she wouldn't care if you blow a load every 5-10 minutes. Please reply back and let me know what happened.