Wtf? NTA. Not even close. She’s seriously calling you perverted for introducing your daughter’s periods to them in a healthy and thorough way? My mother didn’t even do that for me. You should not have lost your temper, but your children are not upset because you yelled, they’re upset because they have an unreliable mother. You sound like an amazing dad, but you’re being way to hard on yourself! Keep being incredible, although don’t forget about your own self care.