Its not unusual to not be able to orgasm during intercourse. Only 30% of women can orgasm from intercourse alone, so I wouldn’t put too much stress or pressure on yourself that you can’t orgasm from just intercourse.
As long as you can orgasm from a hand, mouth or vibrator, I think your orgasm status is perfectly fine.
I’m trying to understand what you are describing, “my torso widens”, which also doesn’t sound too problematic. The muscles of the pelvis can relax after an orgasm, which might make the belly seem wider, but that also sounds very normal.
I’m more concerned about pain in the uterus. I would consider getting an ultrasound to check for fibroids.
You can also consider seeing a physical therapist for them to evaluate the pelvic floor muscles.