period help!? getting worried!?

ok so usually my period is very regular and always comes on the same day but it is now 6 days late. A few weeks ago i was on holiday and i notice some brown spotting that lasted a few days. This spotting cant have anything to do with being pregnant because i didn't have sex whilst i was away. When i came back it was like a week until my period and i did have protected sex and i checked the condom and everything. He also didnt *** in me. I made sure aswell that when i had sex it wasnt when i was the most fertile. Now im 6 days late and im just worried if i could be pregnant or if its just an irregular period, please help!!!