I'm plantation bleeding or early period?

My period due date is 3days away, we had sex the day after ovulation.( We are not ttc right now, but we're thinking of started in 2019, as our first born just turned 2.) I'm experiencing some spotting its brown n I've some cramps, same as I would have during my normal period and my boobs also feel sore...( I completely weaned my baby from breast milk 2 months back). Could it be implantation bleeding? I didn't experience it during my first pregnancy. And I have a partial bicornuate uterus.