Period 2 days late

I’ve had unprotected sex 4 times this month and once during my ovulation window. My period is now 2 days late. Having some tummy troubles and been really tired. Keep telling myself I’m tired because I have a teething baby that hasn’t been sleeping through the night because her teeth are bothering her. So I took a test this morning and it was negative. My period is always freaky consistent, like same day of the week and same time frame type of consistent. What could be the cause of my period being late, this is very very very unusual for me and I’m a little worried about it honestly.