Could I be pregnant?

I have been on birth control for 2 years now (pill) and I came off of it about 2 months ago. I had what I thought was a period but I'm sure was just withdrawal bleeding immediately, and then I had my first actual period a month later. It was strange because my period lasted about 12 or so days and was obviously much longer than usual. My period ended on 9/26 and about a week later my partner and I had sex and he ejaculated in me about 4 or five times since I got off my period. Since I'm just coming off of my birth control I don't know when I was supposed to ovulate. My next period isn't supposed to start for about 6 more days but I have been having light spotting with a kind of brownish color and very mild cramps, hardly even there. How likely is it that I could be pregnant? We have been trying to conceive and I'm trying to not to be overly hopeful and not just think that I'm having symptoms and implantation bleeding. So I'm hoping that this bleeding is implantation bleeding.