I second the strength training-this small of a gain could just be water retention, but extra activity can't hurt
I input your stats in a bmr calculator, and for your height and weight your basal metabolic rate is around 1300 calories per day. It would be a little more with your activity level, but not by too much. The only way to increase your metabolism is by exercise and building muscle. Have you had your body fat percentage read? Even thin people can have a high body fat percentage, and it takes more energy/fuel (calories) to maintain muscle mass than it does fat mass, so the more muscle we have, the more calories we need to maintain our weight.
My weight loss has been SO much faster since I started strength training. If you don't belong to a gym, try a pilates video for home. I just started doing pilates at the suggestion of another member of 3FC, and it is a GREAT workout and seems to be just as good of a strength exercise as what I'm lifting at the gym.