Frustrating

I have been finding my stress management skills pushed to the max lately. Marley has definantly hit the terrible twos. She wont listen, correction she does listen she just doesn't do as I ask. I know that its probably asking too much but I feel that she is way to smart for me to have to do everthing for her. When she is not listening she makes this aweful 'ah' sound that just makes my skin crawl. When she is really having a bad tantrum she chucks her toys around the room and stomps her feet. I know that its normal and I'm sure that its pushing more buttons than it should but I don't know what to do. Time outs don't work and I find myself constantly putting her there. I've tried spanking her but that doesn't work and I don't like to do it. I can't put her in her room cause she likes it and when I say do you want to go to bed she says yes and will happily go to bed. Don't get me wrong I like it when she goes to bed cause I get a break I just don't think its getting anything accomplished. I know that I am over hormonal right now because I'm pregnant so things are irritating me more, but I am seriously getting stressed out with having to deal with this child. Where did my sweet little girl go???? What can I do??? I will listen to any advice you have. So ya thats me venting thanks for listening.