What’s going on?

Hey Everyone, So July 1-5 I had my normal period . I suppose to got my period again July 26 but it came on the 25 “ a day early” it was unusually light so the following 3 days I was spotting and when it stopped I had sex and it’s came back for few and completely stopped. It’s been 5 days and i have light slight pains/cramps in stomach , breast soreness come and go, and i feel nausea but no vomit! pregnancy test is negative and I’m really confused because this is unusual for me can anybody please help me understand am i pregnant or what could it be?