Rant about step kids

I'm 21, my partner is 25 he has two kids. At the start I used to adore them and now for some reason since being pregnant I cannot stand them at all they are 4 and 6 and seriously little bitches and are exactly like their mother and their mother lets them know much she hates me. Anyway I'm 37 weeks pregnant and don't get any sleep as it is and I have to set the bed up a certain way to get sleep. Well!! I'm sick to death of them both jumping in the bed during the night waking me up leaving me with literally no room at all to even roll over and he doesn't even move them back to their own bed and he knows how much I hate it. If I try move them they pretty much scream the house down or just come back in 5 minutes later! I seriously don't know what to do. And then I just lay here wide awake until morning or I go lay in their bed or the couch and still get no sleep. I'm probably being a cow but I would love to get some sort of sleep!