Help me please, my daughter is out of control EDIT
My 3 year old daughter is out of control. We consistently punish her when she throws her fits. Lately, she is screaming at us, and trying to hit us, and pinches and scratches when things don't go her way. I really don't know what to do with her anymore. My 5 year old son has autism, and he doesn't even behave this way. It is getting to the point where I can't even go out with her for fear she will scream and cause a scene. Please tell me what I'm doing wrong! I put her in time out, take away all her toys, and I'm seriously considering spanking. I really don't want to. Am I the only one with a toddler like this? I keep thinking she will grow out of it, but she will be 4 in October and I'm so scared that this will continue.
EDIT: Thanks for the advice. We have had a better couple of days. I'm trying some of the suggestions everyone has made. As for some of you asking if she has autism, she does not. My 5 year old son has low functioning autism, so I'd know it if I saw it. Other than her tantrums, she is a "normal" 3 year old girl. She socially engages with other children and with adults. She responds to her name and makes eye contact. She has no speech delays, and no fine or gross motor delays. She has no sensory issues. She also engages in imaginitive play with me, other adults, other children, or off by herself. She was potty trained in less than a month. So no autism. No regression of skills. She just has horrible tantrums when she doesn't get her way, it doesn't mean she has autism. Thanks for all your help!