Does anyone have a SO with children. We always seem to get into arguments because his 4 yo doesn't…

Does anyone have a SO with children. We always seem to get into arguments because his 4 yo doesn't listen to me what so ever. She's a daddies girl but I watch her and provide just as much as our own son and today I am just fed up with the back talk and being ignored. Keep in mind I am also raising a 1.5 yo abs 32 wks pregnant but I can't be alone in being frustrated. He says I'm being ridiculous and selfish.