Period help?

I have never been able to track my period so well. I used to get it every month for 3-4 days or so, now I take my pill so I get it every 3 months sometimes I go even more months without it but I got my "period" I think...no red blood but it was very dark and brown and it wasn't a lot and constant just a little over the course of two days. I'm not sure what to think of it. Has this happened to anybody else ever? I don't believe I'm pregnant I've had absolutely no signs. I've been on the pill for 5 years and yes I have a boyfriend and me and him are like bunnies. Just wondering if this is normal.