Try not to compare yourself with anybody else. You're right....Who knows how healthy those "skinny" people really are. Are they eating lean protein, good carbs, fruits and vegetables? Or are they eating fried, greasy, fattening foods? If so, they may appear to look healthy, but inside they may be a heart attack waiting to happen.
Eating right is going to be a major challenge and hard work. If you want changes bad enough you'll do it! Focus on your goals and resist temptations. Take it one pound at a time. Include exercise at least 3 days a week and watch the weight fall off!