Echo. Start losing weight, get out and walk, exercise however you can, change your diet to more healthy fare, all that jazz. The stress will also decrease as you feel better both physically, and self-esteem-wise. As has been said, you're young enough to fix this while it's just a weight thing. Get moving, literally, now.
Yeah, it sucks, and I know that eating what you want to and not bothering with exercise seems more appealing, but you don't want the alternative. The alternative is someone like me comes to take you to the hospital when you have your first heart attack before age 40.
If it sounds like I'm trying to scare you, that's pretty much what I'm going for. Your health is a serious matter, so start taking care of yourself.
You'll feel so much better, overall, once you've started on a more healthy lifestyle.