I need advice

JM • 28 started TTC #baby 1 June 2016. 2 and half years 🌟
I believe I ovulated yesterday 22d as I was really wet, and when I was checking my cm it was very open and I had cm that was very stretchy and clear like egg whites. 
Today is the 23rd and I've dried up as far as I've check, and my insides when I check cm is very closed and feels tighter again. 
When do you know you're 1dpo ? Like how do you now?