Hi Mariella! I am very sorry to hear about your BFN. Those rotten things are never easy! I know what you mean about feeling obsessive, IF has a way of doing that to us. When DH and I see a pg women, we are always joking about me rubbing her tummy. Don't think I wouldn't do it if it would work!

As far as the HSG, I know I had mine done on a specific cycle day, but I can't remember what day it was exactly. Sorry I'm not any help!
Hang in there, don't give up, and you'll soon get your BFP! My parents desperately wanted another baby and 15 years after my youngest brother was born, they had me! My Mom was 40 years old when she had me, so perseverance definitely pays off! I wish you the best!
Kat