Hi,
Whatever happened is in the past, and you really do have to forgive yourself. I'm not sure if your mistake was related to sex, but mine certainly was/were. When I'm (hypo)manic I go into sexual overdrive, and I have several times jeapordized my marriage because of this. The last episode was what pushed me to contact my doctor. Through therapy I've been (slowly) learning to forgive myself, and to recognize that this is part of having bipolar II. It's not a moral failing or some insurmountable character flaw on my part. Please keep telling yourself this. My husband loves me, as I'm sure yours does. What matters now is that you take care of yourself and look to the future. I still feel guilty about the things I have done in the past, but am slowly realizing that they were influenced by something that was largely out of my control. You really do need to forgive yourself, and allow yourself to enjoy the love and support that I'm sure your husband has for you. I hope that together you can work through this depression. I feel your pain and send all my support and best wishes to you.