temp drop 6 dpo?? (bbt chart attached)

I am pretty postive I o'ed on cd15. I know some of you might say cd 16 or cd 17 ... my body tells me I ovulated on cd15... but I could be wrong also. (just glad I ovulated lol)

so I don't think this is an implantation dip because seems early to have that. especially since I am not positive when I ovulated.

i have a lot of ewcm cd15 night, and increased cramping that night. then on cd16 I had more cramps in the morning and then it stopped... by that night I left no more cramps or anything..

anyways.. what could that dip be? is it a fall back rise or whatever its called? a second surge? thanks!