Help bleeding 7 days early

had sex 2 weeks ago and im bleeding 7 days before my period is due first started with spotting as in i wiped and there was a little bit of blood, so i put on a panty liner later when I checked there was light pink discharge on the liner the next day was the same apart from the discharge was more of a Pinky Brown, the 3rd day i had a medium flow of watery blood and again to day, ive not had any major cramps like i normally do with my regular flow ive has a few light shallow cramps and ive been feeling a bit nauseous, in confused due to the fact I'm 7 days early took a test this morning which came back negative (altho I think it may be too soon to test) and should I go to the doctors, can anyone give me advice or has anyone had this happen to them and what was the outcome