Is this implantation bleeding?

I've been on birth control but recently stopped in order to get pregnant. I haven't been on very long and initially wanted to start because of my hormones being wonky, hoping it would level them out. But then we decided we wanted to get pregnant so I stopped. My period was due yesterday and all I've had so far was light spotting that's brown in color and no cramps. I'm using tampons in case it is my period and picks up, but it barely ever has anything on the tampon when I take it out, just a little brown stuff. I've also been super nauseous lately, sore boobs off and on, and extremely tiredness and fatigue. Could this be effects of the birth control and stopping it or does it sound more like pregnancy?