Pregnant while breastfeeding

Anyone here get pregnant on purpose while nursing? But have no period back yet?

I know you ovulate before period comes back but I’ve been using opks for a month and still haven’t caught a surge. Baby is 7 months old and I thought period would be back by now. We want to try for our final babe, our 6th as I’m almost 36 and hubs is 41.

Any advice? Just a waiting game til period returns I guess?