When do u rule out a late period

I was on the depo 3 years. I got off switched to patch and been off all BC for 3 months at least. My periods have been on time to the point to glow. I did my bbt just to see if I am ovulating or if my periods are just shedding my last months bbt below. This month me and my fiancé had sex a couple of times some I logged some I didn’t. I have a late period. earlier this month I had a gush of discharge which I’ve never had but other than that normal. My period is only a day late but it’s weird from the last 3 months when should I rule out stress n other things causing this? I will get a test if I need to later but don’t wanna waste money for a negative lol! ♥️