Dude, you've got your whole life ahead of you. You can make anything happen. Of course you won't realise that until much later. Make a plan and write it down, then stick to it. You don't need any qualifications apart from those required for licencing, but if you want A levels - then go and get them.
Your biggest hurdle is going to be money. Beg, borrow, steal - then use it wisely, go modular. For many it means getting a job or two or three, then working for years to make it happen. (Obviously it won't happen because you'll want to go out and spend it all like every other 20 year old.) Prove me wrong. Stay living at home as long as possible and get the best paying job you can, then go to your local flying school and work weekends for flight time. After a year you'll have your PPL. Get some credit cards for day to day purchases and pay them off every month (to build your credit history) - I would suggest work and save to get your first hundred hours, and only consider borrowing anything after you've passed your ATPL exams.
Everything you want is perfectly achieveable from nothing in 5 years. If you're lucky, you'll get hired straight away. If not, you might have to wait for the next wave to come along. It's not easy, but if you WANT to be a pilot you will be one.