How often to bd

We have been trying for over a year now with 1 chemical only. I use opk and bbt and get a confirmed ovulation every month usually cd14-16. We are so stressed and exhausted from ttc that we really only bd when I’m in my fertile week. Since my ovulation is so consistent, we usually bd every other day starting around cd12 and continue until I’ve ovulated ( maybe do it 3-4 times a month). My fertility doctor said we need to be doing it 3-4 times a week ALL MONTH. My question is why. I know when I ovulate and I’m not fertile all month. Is that really necessary?