No period after IUD removal

Ma

I got my Skyla IUD removed last April after 18 months of use. I haven’t been on birth control since. I got one period in July, one in August...and the last day of my most recent period was October 13th. I’m not pregnant. I’ve been tested for PCOS, endo, thyroid issues, etc and nothing. My stress and weight aren’t causing this. No one can figure out why I’m not getting a period. Any ideas or suggestions? My husband and I want to start actively trying soon, and I’m at my wits end with appointments and negative tests. 😔