Defiant child?

I have a 6 year old boy and I'm having the hardest time controlling him. Anytime I tell him not to do something, he looks at me, rolls his eyes and does it anyway. I have very thin patience, and don't know what else to do except yell at him. Time out doesn't work, sensing him to his room doesn't work, threatening to take away toys, playtime, etc. Doesn't work. I just don't know what to do. He's also started lying. I'll tell him to eat his dinner and he'll get too bites down and say he's going to throw up because his belly's too full and start forcing himself to gag, or he'll pretend to start choking. He throws a fit over anything and I'm so overwhelmed. What do I do?