Hi Army Wife-
My dr. schedules u/s at day 8 for clomid+iui cycles. I don't know if it is standard or typical, but during my last cycle it was extremely helpful. Without an u/s my dr wouldn't have know that my lining was only at a 5. My understanding is that it is difficult to have a successful implantation without at least a 7 and my dr's office has never had a successful iui or ivf with anything lower than a 6. Also, I guess it is fairly common for women who are taking clomid to have an underdeveloped lining, it actually reduces it. I took Estrace pills twice a day and built my lining to an 8 pretty quickly.
Also, without an u/s my dr wouldn't have known that I had 6 follies, which I guess is quite a few for an IUI. I ended up aspirating one before the iui.
My dr told me that follies aren't as "successful" if they are too "mature" and grow larger than 26mm. During the u/s on day 8 she discovered that I had 3 follies that were over 30mm and I still hadn't triggered naturally. As soon as I built up the lining she gave me an hcg shot to trigger.
Due to my positive response to clomid she is lowering my dosage to 50 mg for my next cycle and is planning to do an u/s on day 6 to check the size and number of follies with the expectation that she will have me take the hcg trigger day 8-10.
This is probably way too much TMI. I'm not sure if the extra u/s's are necessary or not and I would think that there must be a reason that some dr's do them and others don't.
Good luck with your hsg. I passed out during mine, but it really wasn't that bad (I pass out during routine pap smears - long story

) I would say that it is less uncomfortable/painful than a regular exam and it is kind of interesting to see what your uterus looks like. Hopefully they will have a screen where you can watch during the procedure. I would take some ibuprofen or other pain reliever before you go, just in case. During my exam the dr found that I had a bicornuate uterus, which I guess is good to know.
Good luck on this cycle. I'll be sending some baby dust your way. I'm still waiting for AF to get here. Isn't it just like that ***** not to show up when you want her too!