What should I wear for our valentines day dinner?

I'm not too sure on what to wear for valentine's day. My boyfriend made reservations at Cullen's, an upscale restaurant at 6pm. I'm not too comfortable with my body since i gained 5 lbs this past year :/ I'm now at 130 and I'm at about 5'2. I'm not sure wether to wear a skirt or a dress.. help :/