14 dpo spotting

So what I thought was my period started on the 10th when it was due on the 11th. I had spotting mainly brown blood mix with a little red and the following day I had the same thing. Both days it wasn't even enough to fill up a pad so I'm guessing it was just spotting and usually I have a very heavy flow during the first few days of my period. So heavy that I have to wear a pad and super plus tampon. Now today I barely have any spotting and I'm currently just wearing a panty liner which has a few spots of brown blood I took a test 3 days ago but it was negative. Going to retest tomorrow morning, has anyone experienced this?