Nervous, worried.

My period is usually irregular, but the last couple of months it’s been on track. Well, this month, it came out of no where, no cramping, no moods swings, nothing. It came 2 weeks early. I’ve been sexually active with my fiancé before my period hit, and we used no protection, I did take a pregnancy test, and it came out negative. This early period isn’t normal for me, all I’m doing is spotting lightly. Now my boobs are sore, my stomach feels tight, kinda nauseous. Do I need to take another pregnancy test or is it just an irregular period?