Quoting Think Bαby:" Oh I only I lived near family or real friends. The only break I get is my one day off during the week and he's in daycare. 3 was horrible too. "
Maybe see if you can pick up an extra day at work and put him in school another day so you have some adult time and time to give your brain and patience a break.
My son was such a breeze until 3. As soon as he could talk he has wanted to test his attitude, and do typical 4 year old things like back talk, not listen, complain, whine. They don't understand the hard work that goes into what we do for them, and it's a hard lesson to learn as a parent not to apply adult logic to a toddler's world, in an effort not to get frustrated.
I promise it gets better.