Could you be pregnant? I would take a test maybe.
Wait at least a week, although all women has different symptoms, it could be that your AF is coming or you could be pregnant and too early to detect the test. It happened to me before also, like red-brownish and it lasted for only 2 days, I went to the doctor and they done urine and blood test but it was negative, I was only 3 days late that time. Sometimes our period are heavy and sometimes barely there, so it make us worried but my advice is don't stress it too much coz it could make your AF delayed more if you are getting one soon. That is what I find out mine, I had terrible headaches, cramps,sore breast and dizziness but it turned out not pregnant, just a little stress and it messed up my period. But every women has different case, yours could be different so wait for few more days and retest again if it will come out negative then schedule an appointment to your doctor, it is best to know what is going on with our body and know the answers we are looking for. Hang in there coz I am same way, though I am 14 days late now, so If I am preggo I would be 6 weeks already, haven't take a test 2 days now because I kept getting negatives so I will wait until I go to the doc on Monday and will keep you updated what will be the outcome. Hope this helps...
it could be implatation bleeding i would do a test with first morning urine in a couple of days gud luck!