Spotting for 6 days - what is going on?

[susan_1981]

I had an HSG done this cycle. I had that done on CD9 and had some light bleeding for a couple of days after, ovulated on CD13 and on CD21 started spotting. Thought my period was coming a week early but no, 6 days on, I'm still spotting. My actual period should be due tomorrow or the next day. I'm wondering if it's related to the HSG. I've tested and BFN so it's not likely that it's implantation spotting. Has anyone else had this?