I'm sure it won't make a difference about the ultrasound, hard not to obsess about everything though! I'm pretty sure I'll test early! With my iuis I did, the trigger was out of my system by 11dpiui or 13dp trigger so if you're not testing the trigger out wait that long before testing, a false positive is not good!
I'm cd1 or 2 today as AF arrived yesterday evening so expecting to go in for my scan and start stims tomorrow, eek! Xx