Stopping birth control/late period

Hello! I recently started trying to conceive. I’ve been on birth control (pill) for 7.5 years. My last period was September 23 and I stopped taking my birth control during that period. My period is now on day 9 of being late. I have taken tests (most recent being yesterday and it was negative). My question is...when you stopped taking the pill, how long did it take for your period to regulate and how late was it? My period has been like clock work for years and now that it’s late it has me wondering if it’s because of stopping the pill after all these years or if I am pregnant and it isn’t showing on a test yet for a variety of reasons. Thank you!!