First off, I just want you to know that no matter how bleak or dim the future seems, know that with Christ there is always hope. Trust me Him. (:
2 Corinthians 4:16-18
Know that you’re loved regardless of what society or anyone else might say. You are fearfully and wonderfully made by a God who’s madly in love with you. He loves you just as you are and whenever He looks at you, He smiles and recognizes that He wouldn’t have you any other way.
John 3:16
Psalm 139:14
Zephaniah 3:17
Jeremiah 29:11
I have to admit, I’m not exactly an expert when it comes to eating disorders (though I have struggled and continue to struggle with my self-image) but here’s a thread on Catholic Answers that addresses some of the concerns raised by these eating disorders and how one can overcome them.
As always, I’d recommend prayer for whatever you are going through. I’m sure that God knows your pain and all the things you’ve been through, and He longs to heal you and help you find your worth. There’s no particular prayer I would suggest, so long as you do pray. Keep in mind that prayer doesn’t necessarily have to consist in stringing beautiful words together or going to church to pray for hours on end. Simply abandon yourself to the love, mercy, and grace of God. Empty out your heart to Him. He will listen.
Know that I’ll be keeping you in my prayers. Remember to smile and be happy because God truly loves us immeasurably and sees the beauty in each and every one of us, and He longs to hold us in His arms, even in the midst of our suffering and trials.

God bless!