If you have self esteem issues, a year out is not necessarily going to fix that.
If you're taking a year out to do something worthwhile - travel, volunteering, placement - then go for it. It will help you realise that your self worth isn't tied up in your appearance and that the world is bigger than High School politics.
If you have no plans- just go to Uni/College. You'll meet new people, maybe join some societies of like minded people. Embrace open-minded folk and get rid of whoever and whatever is dragging you down. You won't have that fear of missing out when you see your peers at Uni etc.