I think you should try just getting inside her, then not moving at all. Just rub her clit or something to make her cum. You can just stay there and hopefully not cum for a while. Once you are comfortable with it, move a little bit. If she's not happy then suck her nipples or touch her clit and kiss her neck and do romantic stuff to keep her happy!

Well, it's just a thought. It might work. I think controlling when you come has a lot to do with tensing your cock or keeping it relaxed. I sometimes kind-of twitch it when it's inside her and this can make her come without me having to even feel anything really (if I want to, obviously).

Basically, I think you should just stay inside her and relax, take your time and not move until you're ready.

Good luck.
(by the way, I don't know if I'm right or wrong because it hasn't happened to me, sorry, but I think I'm kind-of right).