Honestly puzzled...need opinions

Amanda • TTC baby number 3. We have an 8 year old and a 4 year old.
I don't know what to think this has never happened before. I got off my period like normal then three days later I started bleeding dark black to brown blood that was kind of thick and looked like it had mucus in it. Now when I while it's a deep red color still with clear mucus. Anyone have this happen before?!