Implemantation bleeding?

I’m on the pill but my boyfriend came in me a few times and I’ve occasionally missed a pill. I still ovulate on the pill and we had unprotected sex on the fertile days.

Im experiencing nauseas, light cramps, a tight feeling in my stomach and brown spotting. Is it implantation bleeding? If not the what could it be?

We both want a baby but haven’t been trying for one yet. If im pregnant I’d be over the moon. I lost a baby last year so I’ve been trying not to let myself believe there’s a chance I’m pregnant, so I don’t get let down.