First post... Need advice please!!

okay so not sure where to start with this question but I'm gonna try. I had unprotected sex on the 22nd of October and my period was due this Saturday (11th November) but it didn't come! but what I'm unsure about is my periods are messed up and it's not unusual for me to miss a period and then come on the next month when I'm supposed to.. but because I had unprotected sex obviously my mind immediately jumped to the conclusion of possibly being pregnant but idk!! I've spoke to a friend and she told me to wait another week or so in case it's just late and she'll come with me to buy a test etc but I'm so unsure of what to do! like I said it's normal for me to miss a period so am I just worrying over nothing??