Late ... confused

So I’ve been preparing for ivf after an unsuccessful iui and 10ish mos of trying. Doc said I have a small non concerning endometrioma and POSs mild endo. However my period has always been regular to the day- super predictable and totally normal. I’m currently 9 days late and so confused. The only other time I was late was 2018 and I think I just skipped a period 1 mo bc I was under an immense amount of stress.

I refuse to get my hopes up - doc said it was still POSs for us to get preg in our own but it would be pretty difficult. So we hadn’t even been tracking my ovu just doing it whenever we felt like it!

was wondering if anyone else has had a similar situation?? Other causes of a late period? I’m not stressed l, actually pretty chill, just baffled. Appreciate any stories or thoughts??