Wanting answers please?

Shanique
So most of my TTC questions can easily be answers via Google or Glow forums. 
After days of searching I've come up blank on this one. 
Firstly I'm supposed to be going into my fertile stage, all my <a href="https://play.google.com/store/apps/details?id=com.glow.android">fertility apps</a> say this week sometime but different days. I know they can still be incorrect but I trust them as my body is pretty average in the cycle department. 
But I've noticed that I don't have any CM in the past few days and I normally can tell when I'm ovulating because I get really wet down there and then I have one day of really bad cramps. 
But today I've been having these really dull but hell painful aching cramps in one side. 
Also, OPK's are nearly invisible negatives :/
So I guess what my questions are..
What is this pain I've been getting today?
If it's ovulation pain, where's my CM and the positive OPK's? 
Could it mean I'm gunna ovulate soon?
Or is it just unrelated?
If anyone can help thanks :)