Hi Jenjen,
I had issues with my then 3 year d when I was suffering with bad morning sickness early on. She was very challenging, all I could do was tell her the behavior was not ok!!! And put her in time out or tell her she couldn't watch her Dora DVD that night. It seemed to work. I now have a new bub and am using these same techniques, this is not to say she doesn't scream her head off and be challenging occasionally but it's a bit better because she knows we mean business goodluck with it.