Struggling,
I think many survivors, for various reasons, find it difficult to tell their partners. One reason is the one you name: she is the one person with whom you feel safe and comfortable - if she rejects you, you feel you will be utterly lost.
The other side of the coin is this. What is important in the first instance is to face your issues somehow, not necessarily to face them by telling your partner about them. Are you in therapy? If not, I would strongly recommend that to you.
Part of the T's job in your case would be to help you face the problems your relationship with her has suffered in the past, and find ways to overcome those difficulties. If your relationship is in fragile condition anyway, I can't imagine what would be gained by throwing a revelation of childhood abuse into the mix. My thought would be to rebuild things on the relationship front, as well as make progress on abuse issues, and then disclose to her when the atmosphere is not so tense and distrustful.
Much love,
Larry