Endometrial Biopsy

This post is actually just a question for those of you out there who have done an endometrial biopsy to improve implantation failure. Do you do the biopsy the same month as your bc pills or do you have to wait until the following cycle to start bc? AF is making me mad because she loves to stay away when I need her to come and I'm so afraid my transfer will fall right in the middle of the beginning of school. August is not a good month to be taking off work when you're a teacher. I know I can call the clinic about this but I'd rather ask you guys! Also what do they actually do to you? Our plan is to do this along with assisted hatching to hopefully get these next ones to implant. Any advice?