Period or ? :/

My boyfriend and I have been together for 3 years , and Last months period came on the day it was due, and it was only a little bit of blood and mostly brown old blood! It lasted for about 4-5 days which is normal for me. 
I'm on the pill and I am very reliable with taking it everyday, I've been on it for over a year as well! 
Me and my boyfriend don't use condoms, but we use the pull-out method. 
I'm due for my next period in maybe 5 days, and I've had normal period signs like pimples, sore boobs and white discharge, like I always do! (That's how I always know my period is coming)
I'm just wondering if I could be pregnant because of last months 'weird' period? Or has anyone else experienced the same thing ?