Implantation bleeding? Or what

Okay.. I am 22 years old. I always use protection with my fiance, my periods are almost always arrives exactly on time or a couple days before or after. Usually always comes with cramping, bloating, and heavy bleeding the first few days. This time .. My period came a day before my calendar says.

(which is fine) I am on day 4 of my supposed period... and its hardly anything. Its like it keeps trying to start and nothing's happening. Slight cramping I've never had before. The blood is only existent bright red or a dark brown later in the night when I wipe or a little spotting on a pantiliner. Which is never what I use during my period. Could I be pregnant?