Quoting ToriMacias18:" u so all u kno before u sayy its all his fault she knew i was pregnant she is married and has 2 kids ... [snip!] ... me names and saying she was going to beat my A** while im pregnant so i think i had every right to do what i did thank u )"
It's not her responsibility to double check who she sleeps with. She's not the one in a relationship.
Your immaturity is showing.
ETA: So she was in a relationship. Then that's between her and her husband. Your issue is still between you and your boyfriend. Leave her out of it, put on your big girl panties, and figure out if you're committed to fixing this thing and are looking for advice, or if you're here to have women go "smurf that ass hole and kick his ass to the curb." If it's the latter, just do it. If you want genuine advice, stop arguing and listen.