I notice you’re using a single digit thermometer, a double digit is best, they’re not expensive.
Hope I don’t sound patronising but are you putting the end of the thermometer under your tongue and right at the back? Your temp variation it too great to be consistent and to read what’s going on. I can post a picture of one of my cycles if you like, just for comparison?
Sunflower is correct, I get a dip every time at 6dpo but It’s just the time when I would have an implantation if I had a fertilised egg.