How many days should I wait to take a pregnacy test?

So... I've been monitoring my period on this app for 7-8months now and even though I have endometriosis my period is always on time. This month I'm 2 Days late and I don't know if my cycle is changing or if I'm pregnant. Should I test? Should I wait? I'm very anxious and want to test!!! I've been wanting to get pregnant for a while now. Any advise ladies?!?! 
-Thank You in Advance!! ☺️