Ciphers and Encryption

I've made my own personal way of encryption that I will be using with close friends and other classified information. I want to know how secure it is though, that not just anyone can solve it, so here's a message

8x12x16x10x15x24x6x5x9x15x3x15x16x
16x2x7x10x16x8x12x1x22x24x9x13x17

Thanks! If you do solve it give me some tips on how to make it more secure :)
Oh and the x's are just spacers

Seeing as there are now many publicly-available reviewed and tested secure encryption algorithms, why not just use one of them ? With public-key encryption you don't even have the problem of key exchange.

Anytime anyone has tried to use their own secret encryption scheme for things like document or archive passwords, it has usually turned out to be easily crackable. Encryption is hard to do right.

I am sure that a person known as a code breaker could do it in a flash or use a computer to undo it but if it is just chat why bother?