Had sex around the 18th Dec. ovulated 22nd Dec. my period was do the 5th of January but came the 1st... I thought. Only it was light pink when I would wipe after urinating and lasted three days, the last day being a brown colour as if you're uterus is titled from extreme work out and excess discharge from old periods comes out. My workout regime has not changed so it wasn't that. I've been feeling very nauseous and having headaches and lower back aches with mild aches also on the left side and heart burn like a b*tch. Is it pregnancy or something else?? Please help

Oh, and had sex the 4th and It was a feeling I never experienced before, so amazing which makes me question even more, I know sex feels better when pregnant...