Cycle post-IUD

Hi! I’m new with posting so not sure where I could put this but was wondering if anyone else has experienced anything like this.

I had my IUD removal at the end of July - husband and I decided to start TTC casually. I did have a period earlier than expected in August ( even for my IUD cycle which was regularly 25-28 days ) which my obgyn said was normal, then next cycle started Wednesday the 13th, steady bleeding throughout until Friday afternoon / evening. Nothing since then.

So I’ve been told my cycle would go back to what it was before IUD - but I’ve been on various types of the pill for 15 years so that’s hard to predict anyway. Was wondering if anyone would know why I’d go from a heavy 7 day cycle to 3 days?