You could spend some time not perpetually diapered. That always helps retrain some resistance.
Another option I find fun, equally embarassing as having such a problem in the first place, is desperation play right before I stop wearing.
Instead of letting it all go immediately, just hold it for a while. At first a half hour or so, then a few hours, then many hours.
Letting it go in the diaper after holding it for fun of course. Maybe after making it to the bathroom to make sure you can. The idea is just to make sure you can hold it and notice it.
Once you can surely hold it on command and definitely notice it coming, you can work on diaper conditioning. Wear and don't wear completely at random and make sure you follow rules for each. Let go in the diaper, hold on outside.
Learn by feeling to automatically do what your underwear allows.
Become a 'Diaper switch'.