Late period negative tests

So I started my period last month in January on the 21 just like I did in December on the 21 well I had unprotected sex on the 31 of January and the 12th of February I’m not too sure when I ovulated I have a 31 day cycle but I am now 11 days late I’ve taken 5 pregnancy test and they are all negative I have no signs of being pregnant or my period coming I’m cramping a little here and there but that’s about it do you think I’m pregnant or my period is just late cuz of stress ? I’ve never experienced this before with my son I was 8 days late tested and got a positive how long is it normal to be with out a period ? The month is almost over and still nothing