Hi DazednConfused - it sounds like your insecurities are really interfering with your relationship. You have to allow yourself to trust her. (I"m guessing she has done nothing to warrant your mistrust?)
My husband used to feel quite insecure. Trust has grown over time.
I wish you both the best, but try not to allow your insecurities to result in bad behavior: you don't want to be unlovable, and drive her away.
And no talk of harming yourself. She is with you because that's what she wants: you. Now, work on strengthening your relationship by working on your self esteem. Next time you're tempted to say something nasty to her, stop yourself, and remind yourself that you're really feeling bad about yourself and that she doesn't deserve to be on the receiving end of that. Then give her a hug and tell her you love her.