((((Evening)))) - I'm sorry you're so down on yourself ATM. Is there a chance you might be suffering from 'Body Dysmorphic Disorder'? When you look at past friends on Facebook, they most likely have touched up their photos too. I blame most of this pressure to look good on the beauty and film industry - constantly pushing that perfect unattainable image.
If there's something you can truly make better, such as teeth, ears, etc - then I say go ahead and fix them. I'm also all for emphasizing what you already have with make up and hair. Everyone has something that's beautiful about them, so you need to emphasize those good points. Another point that's very important is self esteem and confidence - I've seen some not so attractive people on TV, BUT they have confidence/charisma which equals magnetism.
Just be the best that YOU can be and don't compare yourself to the edited photos on Facebook. Start exercising and get yourself back in shape - you'll feel better about yourself. Remember it could be worse - I often use this Iraqi war veteran as an example. He suffered 3rd degree burns from a bomb blast - ended up with no hair, no ears and severely stretched skin. But he still had this charismatic personality and it magnified his dark brown eyes and beautiful smile.
So I think you need to work on what you can reasonably improve, accept what you can't and love yourself. Make your body strong which will boost your self esteem. Don't compare yourself to others and don't fall for that perfection of beauty lie the beauty and entertainment industry pushes. Here's a good website that talks about real beauty: click on 'Campaign For Real Beauty'.
http://www.dove.ca/en/