Good luck minimatron with your scan!

We are in the process of trying for a girl after having 2 boys.
Im on calcium and magnesuim and we are about to start dtd in this cycle.
My only problem is im never 100% sure when I O. I have been charting and temping but its so hard to know how long to dtd up till without it swaying too much for a boy. Going by my previou charts on average I O about CD18/19 so will dtd the up till CD14.

Also i must admit im nervous about going from 2 kids to 3....is it scary??