Why are my temps looking so zig zag after O??? New to this

Brianna • Mommy to a girl born 9/12/2008.😇 10/26/18. MMC 5/20/19 🤰🏼 🌈 due in April 2020!

I use a fertility monitor. Just wondering if my chart looks normal or what is going on?

anyone have any insights. Thank you