going without the OPK!

I'm TTC and all I am using is this glow app to help me with my fertility window. 
To be safe, we've been have sex everyday or every other day since the last day of my period. 
I heard day 13 of your cycle is one of your highest fertile days which is today for me, is that current a lot of the time?? How long should we continue with the BD?? Any other tips other than using the opk?!?
Please share!