I had an HSG done last year and the clinic were very specific in saying that it should be done on day 10 of your cycle. After AF but before any potential ovulation.

I actually fell pregnant that cycle, following the clearing of the HSG but unfortunately miscarried.

The dye doesn't cause any problems because it all just comes back out or absorbs. It's non toxic.

Good luck hun, and sorry to hear about your ectopic.
Sue xxx