Okay sorry if i'm wrong about this but I believe with strings it starts with 0 then adds up. So if you have a string of Hello, that would be occupied in the 0, 1, 2, 3, 4. 0 being h, 1 being e and so forth. i'm not sure if this would be causing you're problem or not due to the fact that i'm not too experienced, so if not sorry.
