My 4 year old *RANT*

I have a 4 year old, and she does not listen to me. She'll listen to her dad because if not he'll just spank her or pop her mouth for talking back or smack her on the hand for sneaking things, she gets upset but then does as shes asked. After we ask her if she knows why she got spanked and usually she'll say because she wasn't listening/ gave attitide/ talked back and then she'll apologize. However if I do it, she'll continue to give me attitude and be nasty to me and continue to not listen until I boil over in frustration and just give up. I dont want to be too hard in her but I'm not a push over either. But the second I reward her for doing something good it's like she thinks she owns me (not trying to be funny). Its not until I whoop her booty a good 2 or 3 times that she'll listen - most of the time. I just dont know what to do I dont want to be mean but I cant really be nice mom without getting stomped on to which her dad responds, "just spank her?". It doesnt work for me and I've also tried time outs, taking toys, taking her t.v., no sweets, and ive even tried talking calmly to her on her level. I'm 22 weeks pregnant and stressing out that I'm going to have to deal with a kid who doesnt listen to me and a newborn. Yes, her dad/my fiance helps and will absolutely step in when I ask or when hes sees I feel defeated but I dont always want that. I WANT HER TO LISTEN AND RESPECT ME THE SAME DAMN WAY. I'm so tired and feel like I just can't do this sometimes.. she'll even listen to my dad and step mom.. but with me I feel like it's hopeless.