Hi there,
I've had a HSG. I took a couple of Nurofen beforehand, expecting it to really hurt and basically didn't feel a thing from the liquid going through (I obviously felt the speculum, etc - that bit was just like a long smear test). From what I can make out, if there is some debris or a blockage there is more likely to be pain as they try to force the liquid through. Mine whooshed straight through and I really couldn't feel it. I thanked the woman who did it profusely afterwards! She told me that she had had one herself and tried to be as gentle as possible.
You should be able to see the screen while it is done. Officially I don't think they are supposed to tell you the results but the woman doing mine was lovely and I asked her to explain to me what I was looking at on the screen and she pointed out the dye spilling out of both tubes, so I knew it was ok. I also had a long wait for the follow up appt.
I took my husband with me because I was worried I would be in pain afterwards, but sent him off to work as soon as it was done, and walked the mile or two home by myself - it was absolutely no problem. I had no soreness afterwards and we were back to dtd within a day or two.
I found it pretty undignified. There were 3 people in the room (one woman, two men) and it was the first time I had been legs akimbo in such a "busy" room. Now I have been through IVF it seems like a walk in the park, but at the time it did make me uncomfortable. As you have been through childbirth, you might be less bothered than I was!
I think all fertility investigations are quite highly emotionally charged. The nurse who was at my head end said that he hated being on HSG duty because it's so hard for the women going through it (and i expect he has to spend a lot of time calming them down!).
There was one lighthearted moment in mine - the hospital fire alarm went off briefly. Fortunately it stopped, just as I was wondering if I was going to have to waddle outside in a hsopital gown "wearing" a speculum...