Hi all, this is my first post so bear with me

I'm 37, ttc our first child. We had a freeze-all egg retrieval done in March and I was scheduled for a laparoscopy/hysteroscopy in April because I had a couple of fibroids and some scar tissue after a previous fibroid surgery four years ago. During the surgery in April, my doctor found some adenomyosis in addition to the adhesions and fibroids.
After 3 months of healing and only two semi-wonky periods, I started the FET process with only Estrace. After two weeks and a lining still not quite at 7, they found some fluid in a "pocket" in my uterus and decided to stop Estrace (they thought my body overreacted to the estrogen and produced too much cervical mucus), do a quick in-office hysteroscopy to remove the pocket of scar tissue, and then start me on Letrozole instead.
After 7 days on Letrozole, I went back for a scan, and my lining was under 6 and there was another little bit of fluid in there. WTF? They kept me on the Letrozole for another few days, brought me back in, and the pocket of fluid was of course still there. I arranged to have it aspirated the next day and when I arrived, the fluid was gone! Great, right?? Only the bad news was, my lining was only at a 6. So the transfer has been canceled and we're starting over once I get my period.
My question is: Has anyone struggled to get a thick lining, maybe after a surgery or just couldn't get there in general? Has anyone had unexplained fluid in the uterus?
Thank you for your input!
Re: First FET canceled for thin lining/fluid in uterus - anyone else had this?