It’s probably a factor of stress that is self-perpetuating. Once he “lasts long” again, it will be behind him but I personally don’t really care how long I last because I don’t measure my sexual experiences by that.
I think maybe he needs to change his approach and what he finds to be a gratifying experience.
For me, as mentioned over and over and over in this blog, the woman’s orgasm is how I fulfill myself. So if he makes you cum 10 times from oral and fingering and possibly toys, I know you won’t give a shit if he lasts 5 seconds, and trust me, neither will he.
There is such a sense of pride in delivering this to my girl that I guarantee she is not looking at the clock. She wants me to cum, which I always do, but how long I last is not relevant. Sometimes it’s long and sometimes it’s not.
If it was just sex, it would be a disservice to her, but it is never just sex. Make it about the foreplay and you guys will be fine.