Period Late....theories and support, please. 😞

So for years my cycle was thought to be irregular. Well come to find out it wasn’t irregular but rather just slow. I had a period every 90 days. Wonderful when you’re not trying to get pregnant. Sucks when you are. So I became regular on birth control until my husband and I decided to try for our first child. Eventually after a good bit of struggle but blessed to do it without medical intervention, I am fortunate to now have two children. After my second was born, I was regular every 28-30 days for the last two and a half years with or without birth control. I’ve been off BC for almost a year now. My husband and I decided to start trying for our third and probably final addition. Well last month my period was 1 day late. Then I had my normal cycle. Fast forward to now and I’m currently 4 days late. Negative test. 🙇🏻‍♀️. Do you think that after almost three years of a regular 28-30 day cycle, mine has now magically decided to go back to the “slow” 90 day cycle?