Every time I've ever had unprotected sex around the time of ovulation I've conceived. But breastfeeding continuously since my first was born has meant I don't ovulate that often.
#1 conceived first cycle TTC. Stopped pill midway through packet, had breakthrough bleed, ovulated, got pregnant.
#2 conceived the first time I ovulated post partum, which was delayed until 12.5 months due to breastfeeding hormones.
#3 conceived first cycle trying. Had one post partum period at 15 months, which kinda crept up on me and didn't DTD when I'd have needed to to get pregnant. Knew to TTC the next month. Ended in miscarriage.
#4 conceived first ovulation post miscarriage which was 61 days after ERCP.
I'd recommend learning all about cervical mucus, using OPK's and charting your temp to make sure are ovulating and DTD at the right time.