The exact same thing happened to me--excrutiating abdominal pain immediately after intercourse. So bad I went to the er. It was a tubal infection from my IUD. My OB/GYN was there and removed the IUD (so painful) and admitted me for a few days. My first son was 1 yr then. It recurred a couple of times, less severely. I could always tell when it was coming back--I'd get a sharp pain in my abdomen coming up through my rectum when I'd sit down, then a burning pain would linger.
After a few months of that, they did a laporoscopic exam and found scaring. It left scaring in the tubes too; it took 2 yrs to get pregnant with the second of my 2 sons (no daughters). With the first one I got pregnant as soon as I stopped taking birth control pills.
The first son, btw, is about to present me with a third grandchild next month, a girl, after 2 grandsons (whom I adore). I'm so giddy, I was in Macy's yesterday, and after years of looking longingly at all the adorable stuff for little girls, I threw myself into it whole hog. I couldn't stop smiling.
I think that kind of pain can also be from a uti or possibly an ovarian cyst. And insurance-problems-wise, is there maybe a clinic you can go to? At any rate, I hope it either goes away or you can do something about soon. Good luck.