Can only acheive orgasm in one position

I have what I consider to be a pretty serious problem as far as my relationship is concerned.

I can only achieve orgasm from behind (doggy style). I don’t have any sort of ED that I can tell, I just seem to be desensitized enough that other positions don’t work. This didn’t start off as an issue, but my wife has been making it increasingly clear that she’s been missing the intimacy of “having her man on top of her”. From what I can tell, I need pressure at the base of the penis, which is tough with other positions. There may be other positions that allow deep penetration, but I need to make missionary work.

I haven’t been able to find any medical term that describes my problem, or any recommended steps I can take to “retrain” myself to missionary. I’m considering a c**k ring, and plan to swear off having sex the other way until I’m literally backed up enough that I can orgasm missionary. I’m hoping that over time, I can get acclimated if I deny going the other route.

Is there anyone out there that can point me to some help on this subject, or has conquered a similar problem?