It's completely dependant on what you want to do at the end of it all.

Just because your not happy working where you are doesn't mean you have to go to uni to do a levels to be happy. Think of the job you want to do and do whats needed for it.

I'm also 20, never went to do A/AS levels or anything as i wanted to be a spray painter. I started work a month after leaving school and never looked back. I love it, most of my friends that went to college/uni have either left or are fed up with it. And whats more, they can't get the jobs they want or have studied for.