I had my HSG couple of months ago now, a bit like a routine smear test with an x-ray twist. If you get tense about it, it will hurt more. Taking some pain killers before you go is recommended.
It wasn't as bad as I thought- and nowhere near as bad as I expect childbirth to be so plese don't worry too much.
Clomid seems to be the general cure-all they slap you with when they're not sure whats wrong. Even if your bloods are fine, clomid will give your ovulation an extra kick and help you ttc. Good luck!