As someone pointed out, the army is a solution.
Give me a couple of days and I'll see what I can find.
In the mean time I can give you some crazy advice, that is to get a green card to work in the USA, and try to find a job there before you leave.
Some employers might give you accommodation if you promise to work well. There is no use staying in Sri Lanka to earn money there, the wages are way too low.
You can also ask a flight school to work for them as assistant (cleaning, scheduling, aircraft cleaning, oil checks, put the aircraft in the hangar at the end of the day...) in exchange for flying lessons.
Anyway, try to pass your high school (A-level) with a good mark.
You are going to do it the hard way (unlike the mummy & daddy sponsorship scheme) but you will be rewarded: airlines will love your story
