Missed period worry

I’m on the contraceptive pill about a year now but at the start of my last pack I forgot to take the 2nd and 3rd pill, so on the 4th day of the pack I took the 2 missed pills with the 4th pill. That same day I had sex without a condom. Today I was due to get my period (and since starting the pill my period has come like clockwork, coming around midday on the Wednesday of my 7 day break). But now it is Wednesday evening and my period still hasn’t come. So I decided to take a pregnancy test (a clearblue test boasting 99% accuracy from days before the first missed period) and it came up negative. I have been stressed recently about college work, could this explain the missed period or should I still be worried (I do not want to be pregnant).