Why is this happening ?

May 31st- June 4th or 5th I had my period. June 13th I had unprotected sex June 14th I ovulated. June 28th-July 2nd I was suppose to start my period never came prior to this I was nauseous, vomiting and fatigue and I had cramping like I was going to come on I took ibuprofen, but my period never came I was 11 to 12 days late prior to my missed period I took a pregnancy test, but was negative. July 7th-15th I got my period, but it wasn't normal it was light pink then brownish also heavy red then light every time I wiped it was light (tmi). Now August 4th I was suppose to start my period again and now it's the 8th and I'm not on my period, I'm not stressed or anything just want to know why this is happening I'm never late on my menstrual what could this be and no I'm not on birth control.