Try to see if I'm pregnant

Ok so for years I have been irregular bt since 2011/12 I have had a some what regular period I might skip one month out the year. Ok so long story short I have unprotected sex last month in September a lot bt my sex partner has always pulled out, now on the glow app it always a couple of days off for my cycle for example it said the month of Aug I was supposed to come on the the 24 or 26 bt I came on the 30, since I came on at the end of august it said I would be comin on the first week in October it's now going on the 3rd week n I still haven't seen my period should I take a test or wait it out till the end of the month or could this be the month I skip or would September been the month I skip since I came on at the end of august... kinda scared to find out....