IUI please help

I just had my second ultrasound today follicle is measuring 18 mm I am currently on cycle day 12 scheduled to do trigger shot this Thursday on cycle day 14 then IUI scheduled on cycle day 16. Has anyone else had and IUI on cycle day 16 and had Success With It. I'm almost afraid since I don't have issues ovulating on my own that I made ovulate by that time. The doctor said we had a little bit of wiggle room so I'm hoping fingers crossed and praying that I don't ovulate Buy the time of trigger shot