Early period and bleeding gums?

I've been having sex recently with my partner without protection. My periods are normally regular and is normally due for the 21st of every month. I had sex on the 3rd and around the 7th I started have bad stomach cramps and white stuff coming out from downstairs I did a pregnancy test and it was negative then on the 10th had sex again and my period started on the 16th 5 days early along side with that my gums have started to swell, bleed and receed this period I'm having early is really light compared to a normal period and there are not clots like normal it's been four days I'm still on, I also feel sick at time like I get the smell of something disgusting constantly and I feel like throwing up.... I'm not pregnant am I? If i do a pregnancy test when shall i do it? If I'm not pregnant why is my period early i haven't been stressing or anything