I sure know that feeling of not being worth it, it's a struggle. The thing that helps me is to do any one thing that will make you proud of yourself...No matter how small. Then build on that achievement. Those little things add up. Having other people say that I'm worth it is nice, but what really helps is realizing within myself that I am worth it.
One of the little things that helped was setting a little goal anything will do...the smaller the better, and then putting a sticker on my calendar showing myself I did it. I have tons of stickers....depending on how I feel about what I did...smiley faces, frowns, flowers, little sayings like: "good job" or "doing better"
I hope you get to feeling better about yourself because you deserve it.