Had mine a few years ago after being off birth control for nearly 2 years and no pregnancy. XH and I had just separated the month before, but I wanted to have it anyway, just to know if I was ok (it had been scheduled for months).
I had a bit of a tricky cervix, they had a hard time threading the tube for the dye through it. I would say the whole thing was uncomfortable, but not strictly painful. Fascinating to see the dye moving through on the monitor, I was all clear.
The very mild painkiller they gave me was either not-so-mild, or I was just being dozy that day. I took the wrong bus twice trying to get home after because I was tring to save money (should have got a cab!)
I did get pregnant with new partner (now DH2) a little over a year later.
Good luck, just think of it as practice for the indignities of childbirth.