Dear Audrey,
SRS is overrated, even the surgeons who perform admit it is an imperfect surgery.
The reason you may not be able to orgasm with a partner can be psychological or physical.
1) You might be low in testesterone, you can be prescribed just enough to help with your libido and sexual functioning without causing unwanted effects.
2) There are no sexually sensate receptors in the vagina as far as I'm aware. Post-ops usually find their clitoris or surrounding area and the entry of the vagina stimulating. Maybe try stimulating your clitoris during sex.
3) You may not be relaxed enough, foreplay or more of it can help.
4) A patient partner you are very attracted to could be good
5) You know your body better than anyone else, that's why masturbation is usually better than sex or anyone else stimulating you.
You need to remember everybody is different; however, you are not alone, it takes me a long time as well.