BBT Question

This is my first month temping and I was hoping someone could explain to me: why my temp dipped one day and since then it’s been rising. I know I already O’d so I don’t think it’s because of that. For example:

Fri (4dpo): 97.88

Saturday (5dpo): 97.81

Sunday (6dpo): 98.19

Monday (7dpo): 98.32

Is this just normal cycle stuff or could it possibly mean I’m pregnant?