Is it my period starting or spotting?

A few days after we did the deed I've been experiencing lower back pain and weird stomach cramps and then nausea really bad nausea! I normally get my period symptoms which kick 2/3 days before I come on but this time there was nothing like that. I'm due to start my period today there was nothing in my underwear but when I wipe there was really clear wet discharge with some pink. Since then there's been no bleeding. Is this spotting ? Also done so many pregnancy tests before this and all negative!