Started when I was 14 with no financial backing.
At 18 I finally got my PPL (after combining school and working for free for a local flying club 7 days a week).
Coming up to age 27, now a frozen ATPL part sponsored, six months qualified and still kicking around waiting for work.
If you're peed off after three years, try adding another ten to that, and think about how you might feel!!
All the above advice is sound. At 18 you don't have much cash to throw around anyway....this goes on even longer if you go to uni!
Don't let it get you down - I'd recommend you save up the cash and try and finish off in one go. You get better continuity with your training which would ultimately save you cash in the long run..........
Good luck