Yep, I fell pregnant cycle of HSG test. DD is now three, so when I had it done my doctor said that he wanted to check my tubes anyway, but that they were finding people were falling pregnant after the test. Since then he said they have actually published the data which shows it does increase fertility (not sure whether just in that cycle or more longterm?). After having trouble falling pregnant with a second he is advising me to get the test done again. The test I had back in 2008 didn't show any blockages though. Perhaps there were minor blockages that the dye got rid of? Who knows! Haven't had it done again though.
I did find it quite a painful test (although some people don't find it too painful at all). I'm no good with pain!! It only hurt while they were doing the actual test, not afterwards, I just felt sorry for myself. I think it was worse because I wasn't prepared for what it would be like. Doctor had told me I might experience some "mild cramping", but I found it way more intense than that, but only for a few mins. It's also done in a room a bit like a surgical theatre so it's sterile, which I wasn't expecting, kinda freaked me out a little cause I was there by myself. So my advice would be to take someone with you for support and maybe have some pain relief beforehand?
What I had to do to organise the test is get referral form from doctor, then ring up the clinic that does it and register details. It can only be done on very specific days of your cycle so you then call back when you get AF and can work out what day you can come. It is pretty expensive unfortunately.