My SO is letting everything bother him, hes always causing problems, and making them big.

Yesterday i was feeding my 2 week old preemie baby, while my 1yr old and 2 yr old are playing. SO is on his phone, listening to music, and doing whatever. My 2yr old kept bothering his lil bro, laighing hysterically, making his lil bro cry and scream. Im constantly telling him to stop, but he wont listen to me at all. My SO told him to stop and he finally stopped for a bit, then resume. My SO began yelling at me, he accused me of not changing my 1yr old diaper, when i just did it before feeding my preemie. Then, he accused me of not telling my 2yr old to stop, and just sit there ignoring it. Ive told him that i just changed his diaper and i did tell him constantly to stop but he wouldnt listen. And ask him why he wont help me, he expected me to feed my baby while taking my 2yr old away from my other child. He began talking over me loudly, told me im stupid as fuck, and ignored me. Telling me hes not gonna talk to a stupid person like me and turned up the music in his ears.

He didnt talk to me for that night and did his own things like i dont exist. He emailed me musics about how he has a bad wife, whos mean. Musics about missing ex, cause they love him more than i do. Accusing me of cheating and having someone else thats why ive changed.

Idk anymore guys, all this makes me go so insane. I am also in post partum, i get super moody, and my emotions fuck w me. Like i have post partum depression. I am not who i was, i see that i get more angry and frustrated everytime, i do things i dont normally do. Ive talked to him about it in the past, and he didnt give a ratass about it. He just accused me of falling out of love thats why ive changed.

What am i to do?