High bbt and negative hpt?

I was on here a couple of weeks ago and was sure I missed my ovulation day. Now I am 17 dpo, with temperatures that are still climbing. I took an hpt yesterday, and got a bfn. Would anyone know why my temperature would stay high for so long and get a negative on an hpt? It appears that my temperature dipped 13 dpo, and now my temps are climbing. I ovulated on the 10th day of my cycle, and had 3 days before ovulation and the very early the next morning after ovulation. Has anyone ever experienced this on your bbt chart before?