Sorry to hear things are still not working out. I too had that X-ray with the dye in my uterus, and it showed nothing odd for me. They are looking for blocked fallopian tubes or fibroids in the uterus, or an odd shaped uterus. The next step after that my OB told me was to get a Laparoscopy to look for endometriosis or go straight to IUI/IVF. He also had me start on Clomid every second month. I chose the Laparoscopy and they did find some mild endometriosis, and cleared it out, and I got pregnant 2 months after that. And that was after 2 years of TTC. So if your X-Ray shows nothing, I would say the Lap could be a good next step, maybe try clomid too? I had no symptoms of endometriosis, and it was mild, and I have heard it can come about as you get older, and after having previous children.
Good luck, I'm hoping all the time that it works for you and you have a great pregnancy!