Welcome to iMore! Definitely listen to the advice @bamf-hacker gave you. Your watch is still covered under Apple's limited warranty, barring anything you could have done to void it. Contact Apple Support or take your watch into an Apple Store if you think something it wrong with your watch's battery. I've only had mine for a few weeks but I haven't had to charge it during the day. I'm going on 12 hours of use and my watch battery is at 61%.