A little frustration with my scale

It's not moving.  If anything, it's been looking up a little.  I don't get it.  I'm doing cardio, watching what I eat.  Maybe not getting enough water?  Maybe a little too much salt?  I really wanted to be down another pound before going to Vegas, but that doesn't look like it's happening.  I think I'll have to watch it a bit while I'm out there - not indulge as much as I would have liked.  Then come home and get right back on the wagon.