I feel too fat to wear anything but jeans? Help?

So for years I've only felt comfortable in jeans. I'm fairly over weight, and have never thought I'd look good in anything that shows off much. My problem now is that I have a job interview and my friends say jeans are a bad thing to wear to a job interview. So my option is a skirt of some kind. They suggested a knee length pencil skirt. I don't know how that would look on me. Opinions? Should I avoid a skirt like that?