Why would I be spotting now for 3 days? It started 10 days after my last period ended. First it was…

Why would I be spotting now for 3 days? It started 10 days after my last period ended. First it was reddish pink then went to brown the last two days. This is not normal for me. I also feel a little crampy on and off. My period is always regular and on time. I looked it up but there are so many reasons that it could be happening, but none seem to match up to why it would be happening to me at the moment. Tmi... but there is no bad smell to it