Idk what to do with him (fiance).

We have a 3 week old, he has a 9 and 11 yr old from a previous relationship. I go back to work next week. I'm taking care of this baby 100% by myself. I give him the baby to hold while I cook dinner for the family or go to the bathroom and he takes him and stares at his phone the whole time. I freaking hate his phone he's ALWAYS staring at it. I finally put boob milk in a bottle and first, he can't feed the baby cuz he has to go to the bathroom, then the kitchen then the bedroom then okay, and still no attention to the baby, just the tv and his phone. I'm bout ready to flip. I'm about ready to leave. this has been on going. we can't do ANYTHING without him being on his phone. I'm breast feeding so I have to feed him however, baby is crying and I say well. there's milk in the fridge and he ignores me and continues to look at his phone. we cloth diaper and I change the baby, I bathe the baby, I literally do EVERYTHING