Implantation bleeding?

Melissa • 25 and pregnant with our first little Peanut!
My boyfriend and I haven't been using contraceptives for probably 4-5 months now. My periods been off for the last few and every time I get bfn's. Now I'm spotting about a week before I'm supposed to get my period but it's not blood, it's light brown fluid. 
​Could this be implantation bleeding? I've also been having waves of nausea and have been extremely sensitive to smells.