How about getting your woman to perform kegels to tighten up? Approach the suggestion properly of course. Or even kegeling while you’re having sex, that always feels good.
When I’m having my difficulty to cum days there are a few things that help me.
First thing is just rest. I can enter sex feeling like I could cum in a minute if I just pumped away. Since I don’t want to do that I take it slow and eventually I just become less sensitive and not trigger happy. Then I’m in the boat of not being able to cum even if I work hard. So I just take a rest in or out of her. Since she’s been pleased by now when I go back to work I go back to work for me and me only. Get that nut.
The other thing is position and it works even better after rest. The position could be a position that feels good, extra pressure, or one that allows for quick thrusts without getting fatigued. For me that’s a lying down doggystyle as I can thrust fast and not get tired, but it has that tightness I find in doggystyle.
Or even better is me on top with her legs bent up and held above my arms. It lifts her ass off the bed a little bit and makes my cock go right into her g-spot. I find it to be a great sensation and the fact that it gets her moaning and squeezing puts me over the top. I also kegel when I need more help, but that position usually does it without the need.