To start, I don't have a hard time getting hard at all. I've been with my gf long distance for a couple months now and the sex is amazing. Before her it had been about 10months since I had sex and I would get the feeling to cum within a few minutes, so I have been practicing edging (manually) in the weeks we spend apart so I can last longer when we are together. Last night we had an amazing hour long session where she came multiple times (which is always my goal) and during it I'd have to slow down or take a break for a few seconds to allow myself to calm down so I wouldn't cum, but I started going soft near the end of our session and eventually had to give up cause I was too flaccid to do anything. This has happened a couple times before (once with her and once with another girl last year) and was just wondering if anyone knew why this happened and if anyone else has experienced this. Am I tricking my body into thinking I've already cum by edging during sex so I go soft? Or is my body just getting exhausted or something? I do fap 1-2 times a day (usually when I wake up and when I go to bed), so would that have anything to do with it (desensitization-wise)?

Thanks fellow men