Prayer is not a sign of disbelief in God but the opposite. We pray to God to thank Him for giving us all we have, and we ask Him for his Help and Guidance in our lives.
It's a bit like asking your boss for a pay rise. If you want a pay rise you wouldn't go and ask a person on the street to increase you salary it would most likely be your boss or manager.
In a similar way you ask for help from your Creator - God.