Aww i'm sorry sweetheart
But please don't let this one bad experience discourage you from fish in the future- my best guess is that he was just diseased/sick to begin with honey- it's not ya'lls fault. Definitely continue to hang around the www.aquaria.info
site and read up more on the betta sections and others! They're so good- if you decide to get another fish- you'll know what / what not to look for and be armed with tons of great advice!
If need be too- i'd be happy to walk you through things and help you cycle your tank/etc!
I just added to my betta tank tonight (ghost shrimp) so i'd be happy to help you if you decide to try again
You took the best care you could have of the little guy- he was lucky to have you taking such good care of him in the short time you had with him.