waiting until the day of positive opk to BD?

Can this decrease my Chances in anyway? I planned to wait for my positive opk then bd that day and the next two days. I just don't wanna burn my boyfriends sperm out before I'm even at my most fertile point. But I've read that bd'ing before your positive opk is important too. I usually get my positive opk on cd 17 or 18. Is it best to BD from cd 16 til 19? Or is waiting for my positive opk fine?