How to discipline a hardheaded 2 year old?

My daughter is 2. Boy, she is something else. She's really stubborn, and bossy already. She tells us what to do, like "Get out, now!" or "Don't tell me hush!" She fights me on every little thing--what to eat for breakfast, getting dressed (I have to re-dress her at least three times a day, she takes her clothes off all the time), lunch time, play time, nap time, especially BED TIME. Lately she has started spitting... she is just a little terror. Nothing seems to get to her though. She ignores me when I nicely tell her to stop, two or three times. She screams bloody murder in time out--people say put them in a chair, yeah right!! But it doesn't bother her, she'll come out and do exactly the same thing. There are days she will wake at 8am, not have a nap all day, and not want to go to bed at 8pm (her normal bedtime). I'll put her to bed and she will scream and scream for up to two hours. I love my baby, but it really is exhausting to be with her all day, every day, and I NEED her to take a nap, and go to bed. I know someone out there gets what I mean! She will destroy a whole room in less than 2 minutes. I told myself I would never --I've tried it with her and she doesn't even flinch. So I don't even try that anymore--I try getting down to her level and looking at her, and telling her why she is not allowed to do/have whatever, and time out. Nothing seems to work. I don't like taking her out in public, she misbehaves so badly, and screams so loud. And car rides.... are pure hell. Honestly--she screams at the top of her lungs as soon as the straps are fastened, to after she gets out of the car. Help!!!! I am 8 weeks pregnant and so, so sick. This morning she clapped for me and jumped up and down yelling "GOOD JOB MOMMY!" while I threw up.. lol. She is a mess.