My dear friend, I can see that you feel awful and your self-worth has been destroyed by what happened to you. But you ARE worthy and you deserve love and compassion like the rest of us. Humanity doesn't consist of perfect human beings and "the damaged rest".
If you want change, then go get help. Take little steps first, maybe make a doctors appointment and try something to get out of the depression, maybe even meds as someone above suggested. Try to take control over the things you actually CAN control. Be good to yourself please.
You are not alone, and I think you need help to get out of this. Maybe also a self-help group would be good for you, so you don't feel so alone in this? Ask the internet if resources like that are available where you live.
I know it is so very very hard if you have been hurt and are afraid people might react badly again. But not trying/giving up is not an option! Okay?!?

And I am sorry for your loss. I am sure your friend knew that you were there for him/her and it is sad and I understand that you are grieving. But it isn't your fault either. The best we can do is love and when we lose someone, it hurts like hell. But it is a part of life. It sounds to me like the loss of your friend caused some of this anxiety or brought things up again that you carry with you. I hope you find some comfort and support.