Frozen transfer—what cycle day did you start estrogen?

I finished birth control 9/11. I’m starting to spot so I’ll have my period in the next few days. Baseline is 9/17 and I’ll start estrogen 9/18 if everything looks good. Say I maybe end up starting the estrogen cycle day 4 or 5..I feel like that’s late. We did this protocol in August and my lining got thick but never had the 3 layer appearance. I’m wondering if the start of estrogen has anything to do with It. I’ve never had lining issues in the last and that was my first FET. I got pregnant with a fresh transfer and had 3 layers, ended up miscarrying though