So I have a three month old baby he's almost four months. I'm breastfeeding and recently got the mirena. I've been bleeding RED ever since, normal bleeding. Me and my boyfriend had sex Tuesday and now my bleeding has changed to brown. Obviously he cummed in me. But could this be implantation bleeding even if I have the mirena. I've had that feeling the same as I did when I got pregnant with my son. Advice please?