SOS! Help me :(

My dd, who just turned four last month, has been a complete NIGHTMARE for the last month and a half or so. I'm assuming it has to do with the fact that I'm expecting another baby, and the fact that her dad has been taking "business trips" to LA for weeks at a time. She doesn't listen, kicks and hits me, mocks me, talks back, screams etc. I've tried time out, taking toys away, talking to her... but NOTHING works. I come from a Mexican family so all they say is to spank her but I can't bring myself to do that, I don't believe in it and getting spanked as a kid never worked for me. I need some advice cause I'm exhausted!