8dpo my chart - clear ovulation, dip 7dpo

Carla • MC 30.08.18 MC 14.02.19 Rainbow baby Roman born 10/12/19 TTC 2022 Ectopic sept 14.09.23 TTC 2024

Last month I had a dip at 8 dpo and wasn’t pregnancy related. This month I have a much bigger dip and rise than last month at 7 dpo. Now I’ve heard about a secondary estrogen surge, my question is can that happen on any day as in can it vary from dpo to dpo each month? Or can I be hopeful that it could be the myth of an implantation dip? 🤣