Late period

So my period is 11 days late and there is no possible way I'm pregnant because my partner is currently over seas so I'm not worried about that

I know it will come eventually but I'm just a lil worried that like it will come and not leave for a month or something

I'm on anti biotics at the moment, pretty damned stress and have been exercising, I've never been this late before but could those be the reasons it's so incredibly late?

I know that those factors can make it a few days late but this late has me a bit worried something may be wrong with me because it has never happened before

Thanks :)