You are 18 and been working professionally for 3 years. Well done. All said and done this is what matters. Real life experience over university education.
One thing for GP to consider: I did the exact same thing (worked for three years in software development), but now I’m back at school in college. This obviously depends on if you think school is worth it (I did), but I wouldn’t be surprised if my work experience before college helped me stand out in the application process.
Either way, good luck!