Decreased milk supply after ovulation 😕

Aria

My daughter is 4 months old and basically EBF. She has had the rare bottle of formula here and there. Maybe 4-8oz total per week on average of formula. She nurses every hour or two during the day. She doesn't sleep through the night yet and still wakes every 3 to 4 hours at night to nurse. Somehow despite the frequent nursing I'm fairly certain my body is returning to fertility. I noticed a dramatic uptick in my sex drive about a week ago. It was accompanied by tons of ewcm so I decided to do an OPK. Surprise the OPK was positive (test line as dark as the control line). A day later my cm went to creamy, my sex drive disappeared and my milk supply decreased. Along with those changes I also started having some nipple tenderness that I previously (before pregnancy) got after ovulation. So yeah I think I ovulated and I suspect that is why my milk supply has gone down. I can't think of anything else that has been different. My daughter isn't nursing less. I'm staying hydrated. I'm eating plenty of calories. There is no reason for my supply to be going down except for hormones or something.

I read taking calcium, magnesium and zinc can help with cyclically based supply drops so I started taking that this morning. Is there anything else that I can try aside from the standard recommendations like pumping more after feeds and maybe eating oatmeal or drinking a nursing tea. I would love to know what worked for any of you lovely ladies!

Also, if I were to get an IUD would that fix this issue since, theoretically, I wouldn't be having menstrual cycles anymore? I've been toying with the idea of getting an IUD anyhow because my husband and I aren't exactly ready to have a third baby just yet.