My Period Was 23 Days Late. I Was Spotting Exactly

My period was 23 days late. I was spotting exactly 2 and 3 weeks from when I was due both times just for one day and mostly one time. Last night after intercourse I seemed to have gotten my period, looked like normal period blood but stopped and now today the next afternoon it's a brownish purple color and really light. What is the problem? It's making me nervous and I don't know what's going on. Also I've been having shooting pains on the left side of my abdomen/uterus area that comes and goes but only lasts a second. I took 6 pregnancy tests since I've missed my period including one at the doctors all negative and a blood test that didn't come back yet. If anybody could help me out that would be great thank you.