Period late...

Elizabeth

Okay so my boyfriend and I last has sex I Friday and he cummed in me and before that we had sex last Sunday and he cummed in me, both days were like a week after my ovulation period had ended... I was supposed to start my period yesterday...

Note: I got super sick and had to take antibiotics

Don't know if that has to do anything with it though, should I be concerned that I am late on my period?