Tarja, there’s nothing wrong with your boyfriend’s unexpressiveness. And you never said there was. Your feelings of frustration with this are valid and justified. Neither of you are wrong, hence the apparent impasse.
Thank heaven you two have good communication about this. That’s the first necessary ingredient for a solution. Next is the willingness on both of your parts to work on this.
Somehow you’re having sex with him and its successful on some level, despite your frustrations. You’ve had to deal with the frustration up until now, so just keep doing what you’re doing. Next, recognize that there is a part of your brain that realizes that in the big scheme of things, (your overall relationship, health, money, happiness, family, etc) this isn’t that big of a deal. Yeah, there’s that other part that can’t get past this but put that part to the side for a moment and focus on the other part that’s able to keep this in perspective. Focus on this part and make it your dominant frame of mind. Convince yourself, even if only temporarily, that this is petty. Which you know it is, yet its important to you which means its not petty, and ‘round and ‘round you go. But just try to have a sense of humor about it and tell yourself this is petty, focus on that half of the equation.
When you’re deep in that frame of mind, talk to him about it again. Explore different ideas you guys can try like have him do one slight subtle movement or gesture when he’s about to blow, even if making the movement spoils the moment and causes him to not nut at that moment. Eventually I hope you’ll be able to discover that there’s one part of his body that can deliberately move at the moment of truth.
Somehow he’s conditioned himself that as he hits the homestretch the only movements he makes are the minimum to keep himself alive and to keep progress towards the objective. Any other movement is not allowed. Somewhere there’s a weak spot. The possibility of him moving his hands or feet may be out of the question, but he may be able to blink his eyes. Facial movements may be impossible, but maybe he can vocalize something even if its just a soft grunt.
Try to have him abstain from sex for as long as he possibly can. That will at least put him into a condition where orgasm will come a little easier without an ideal situation. If I’m having sex for the third time in one day the wrong song on the radio can spoil the mood but if I haven’t had it for weeks then only real danger can slow me down.
So if he’s really needing it bad, he may be more able to finish in a less than ideal condition, which for him would include moving.