Period or pregnancy???

Hi guys! so on the 27th of May I had sex which was the day before I'm supposed to start the sugar pills & I can't entirely remember but I think I missed Thursday's pill so I took it Friday anyhow I'm up to the period section of my pill packet now and I usually get my period Tuesday/Wednesday & once before Thursday morning but it's now Thursday and all I've got is some dark brown spotting on my pad & when I wipe there's a fair amount of dark brown (I'm guessing blood) 
I have had the dark brownish very light spotting kinda thing on a period once before but this time my period is even a day later & im confused 
& in advance please don't tell me to take a pregnancy test because yes I am going to, I'm just worried and seeing if anybody else has experienced this before & what it meant to you?? 
Also I have been extremely stressed this month and have missed a few pills throughout the month so I'm not sure whether that's contributing anything but thankyou!! 😊