I feel like I'm 9 years old again with messy hair, buck teeth and unstylish clothes wondering if anyone will ever like me.
Ummm...I think you answered your own question. Her abandonment is stirring up your own unresolved issues from childhood. It's not all about her at this point - it's about your feelings of being unlovable.
Was just talking with someone else about a book by Richo called When the Past is Present. About how childhood issues affect our adult relationships. I haven't read it, but read another book of his - How to be An Adult in Relationships - which was marvelous. You might check out the first book and see if it sounds familiar.
Also - although it's not a bandaid and you need to work on resolving your issues - but you WILL feel more lovable once you are in a loving relationship again. And that takes going through the yucky process of dating, with all its weirdnesses and disappointments. You may need to start making a little room in your life for that.
