I had a horrible experience with my HSG - sooooo much pain! They could barely finish it - the first try didn't go very well, so he immediately tried again and got some good views but i've never felt such pain (and i've had some horrible procedures down there!). I did have one completely blocked tube and one that didn't spill out so was likely blocked at the top... i'd be willing to bet that had something to do with how much it hurt, because most people i've talked to say they only had mild cramping.
but my pain didn't last more than a few days... i think because your pain is so extreme you should really call your doctor, just to make sure its nothing they're concerned about. Maybe they can prescribe some really strong pain meds temporarily. Or maybe something isn't normal about what you're feeling and they'd want to see you back in.
Good luck! Hope you feel better soon!