Plan B

My husband and I had unprotected sex during my ovulating days and the next day I went and took a Plan B as we have a 6 month old baby and I felt I wasn't ready for another at this point in time.. I week later I bleed for 2 1/2 weeks... it's been 3 weeks now after the 2 1/2 week bleeding and I usually get my period every 21 days. Glow has "predicted" my period to come tomorrow.. this is the first time this has happened and ever experiencing (last time I took was years ago and everything was normal as expected). I told myself if it doesn't come by the 1st of march I'll take a test.. if negative I'll go doctors. Has anyone experienced any of this ??