How many DPO?

Melissa • 29 years old. Been married for 7 years. Rambunctious seven year old daughter. Lost our son at 18 weeks on 09.13.13. Finally got our positive 11.30!! Due 08.16!!
How many DPO can you wait to test? On my happy week now, today is my peak day per Glow, think I could test by next Saturday and know for sure?? Trying for 72 months, 17 of those for a rainbow baby and it'd be awesome for Fathers Day!