Infertility, Secondary Support Group
"Secondary infertility" is difficulty conceiving after already having conceived and carried a normal pregnancy. Apart from various medical conditions (e.g. hormonal), this may come as a result of age and stress felt to provide a sibling for their first child.

I also had the hysterosalpingogram which is the dye test to check if your tubes are open (are you having that one?). It also involves a catheter through your cervix and they inject dye under x-ray so they can see your tubes. It was more uncomfortable than the sono but nothing severe. Looking at the monitor really grossed me out during that test for some reason, that made it worse!
My only advice is to get ready for a crazy month and don't get too nervous because they do these tests ALL the time. Oh, another piece of advice - don't be like me and expect them to come up with some clear explanation of why you're not PG yet! I was sooo disappointed when we ended up with an Unexplained diagnosis after ALL that testing. Apparently the Unexplained diagnosis is pretty common in couples with SIF.
Good luck, you'll get through it!
P.S. I strongly recommend two books to help you through the procedures and the stress: A Few Good Eggs by Julie Vargo and Maureen Regan and Conquering Infertilty by Alice Domar.