As Jibz say, I'm pretty direct
Take it for what it's meant to be - honest advice, not an attempt at saying you're stupid or that what you've made is worthless. Jibz put it a bit more eloquently, and you should definitely take his advice to heart.
But let me elaborate a bit.
The "hard" thing first: your method is not secure, and it is not practical. Whether "secure" matters depends on your threat model, but there are many other solutions out there that are both convenient and offer hard cryptographic security.
And then on to some words of encouragement: playing around with crypto is fun. Try doing stuff on your own, see what other people have done. Optimizing is fun, and going assembly-level with interesting instruction sets even moreso. Don't stop being interested in these things!
The best thing you can do with this NANY entry is to share the code. Talk to other developers. Accept criticism, learn from it. There's a good chance you'll end up learning stuff about encryption as well as optimizing.
For fun, I've attached a couple of files from 1997 when I thought I had designed a super cool crypto scheme.