is my body is just a little confused fron BC or...

So I've been on BC for over 3 years now. Last month I missed a few pills so I decided to start my new pack the following sunday. I ended up bleeding that week that I didn't take any pills. Here I am on my third week of my pills (which is usually the week I have my period) but according to the way my BC is going now, my period will come next week. I've been experiencing some slight cramping, a little lower back pain and fatigue. Is it possible that I'm pregnant or could it just be that my body is just a little confused. I'm kinda worried so if anyone could help I'd greatly appreciate it!