implantation bleeding or ant flo?

I am on birth control & last month my period was a little bit off. It started early and got heavier so I knew that it was for sure a period. This lasted about 4 days a week before I was supposed to get my period and then I got another period on my planned days. I know that birth control can mess with my cycle so I didn't think anything of it. This month about 5 days away from my period I started to get some light spotting and cramps. This lasted for about 2 days . My period is not due for another 3 days and I usually never get pre menstural sympoms like spotting or cramping until I am well into my period or just at the tail end. I don't know what to do.. maybe just wait and see if my expected period comes and test afterwards if it doesn't? What have your experiences been with pregnancy scares.. do you think I should be concerned ?