Period 3 days early?? IB?

So, my periods come the 3rd of every month and rarely is it a day off. My last period was Aug 3rd and lasted about 4-5 days. That's about the average. So sunday evening Aug 30th I started my period and didn't think twice about the date.. then I got to thinking about it and I checked my ovulation dates and was ovulating on the 18th and 19th and those are the only two days I had sex this month, lol. So, I never have a late period...but this may be IB I'm not sure bc as of today Tuesday the 2nd just awhile ago I just had just the tip of a tampon covered with brown blood. When I first started it was just lighter and slower bleeding than my usual periods barely nothing.. then the next day I probably had to change my tampon only about 4 times light medium flow and it was dark reddish brown, toward the evening it slowed down and was barely bleeding. Today I woke up and the tampon wasn't all the way saturated but almost with like dark burgundy red blood. Then afternoon it there was not as much and was brown and burgendy... then all day it has been tapering down to barely any blood that I don't need to use a tampon. I have felt dizzy, hot, and nauseated today all day. No bad cramping during all this just a dull feeling that keeps telling me that this really doesn't feel like my period, but I still have some doubt. With my son I never had IB bleeding. What's yalls opinion? Basically 48 hours of short and lighter period than usual, more brown and dark blood... no clots AND early period?? Help? I'm over here obsessing. When should I take a test??