You aren't going to find a lot of guys willing to talk about their experiences with such a thing because, quite frankly, it's embarrassing. That being said, I know what it is like to be in your position. I started masturbating at fourteen and didn't lose my virginity until I was twenty seven. So, when I finally had sex, I was just unable to cum. Thankfully, the woman I was with was very understanding. I hoped it was just anxiety, what with my lack of experience and all. It wasn't.
Our sex life was very active but I couldn't cum for months. She was getting frustrated believing that it was her fault. I was getting frustrated, thinking that I was broken. But, through all of it, we were very much in love and so she was patient and kind. A friend told me many of the things you've already heard - too much masturbation, gripping too hard, etc. What I ended up doing was cutting masturbating down to a bare minimum (which was easy considering that I was getting all the sex I wanted at that time). Along with that, when I did masturbate I loosened my grip to simulate my girlfriend's vagina to the best of my ability.
Now, doing those things helped a lot, but it still took a couple of months of "getting used to" her pussy before nature took its course and I was able to cum in her. It is just a matter of retraining your body to accept a different kind of stimuli than what you've been used to. Even then, I still couldn't cum without a minimum of twenty to thirty minutes of fucking. And, there is the one silver lining in having a condition like ours - we can last. You are actually lucky in that regard as imagine how much a woman is going to enjoy you when you can give her a good long sensuous fuck without fear of finishing too soon.
I guess I'm just saying that you need to relax. You have to make it a non-issue to remove any anxiety that might impede your progress while at the same time take steps to retrain your body. You can do it, but it is going to take time, and if you've found a worthwhile partner then she's going to give you the patience and understanding needed to help you do this.
Best of luck sir.