How common is natural hyper ovulation? specifically, how common is it for a 40yo woman who is breastfeeding? my cycles returned 4-5 months postpartum and ive since had 19 cycles that resemble my pre-pregnancy cycle?

Hyperovulation would be ovulation of more than one egg at a time, which is not what you are describing. Breastfeeding will suppress cycles initially (how long varies considerably and 4-5 months is within the normal range) but once they resume the breastfeeding no longer has an effect. The cycles may be different from pre-pregnancy but often are little changed. What you are describing is normal.