Good advice in this thread so far, but don't fool yourself - walking is good for you, but not that good. You won't see too many results. I suggest a tougher exercise routine, like jogging or biking. Start slowly of course, but if you have enough drive and keep at it, you'll be surprised how quickly you can improve. I speak from experience - I walked back and forth from school about a mile every day for two years of high school, and it didn't help me get in shape at all. It wasn't until I started doing more exercise that I got better.

But also, as others have said, it's most important to be confident in yourself. Don't think you're ugly.