Clear blue Advanced Digital Ovulation Test

I have PCOS, I take Letrozole on

CD 3-7 and I had an ultrasound yesterday on CD 15 with leading follicle size 18 mm and secondary follicle size 15 mm. I took a trigger shot around 8:30 this morning and I got this around 9:30 tonight. We BD this afternoon. How long should it take before I actually ovulate? When should we BD again? Help!!