Please help

My wife and I have been married for 5 yrs. together for 11. After the birth of our first son she began to act differently. I attributed it to post pardom depression but over time we realized,with the help of doctors, that she is bipolar. We met when she was 19, I was 23. She was the sunniest,happy go lucky girl i had ever met. Shes been on several meds for this but none seem to balance her out. Either they keep her sick feeling or make her like a zombie. In the summer of 2010 i discovered she was having an affair. I figured it was over but we came thru it. But now I believe shes letting the guilt of what she did consume her. She constantly beats herself up, shes a bad mother,wife, etc. We now have 2 boys. Shes been a stay at home mom for the most part. She has worked some but she doesnt do well with people so that doesnt last long. I work 12 hours a day 5 days a week and 10 hours on saturdays, so im not home often. She does aknowledge theres a problem and I believe this is a good thing but Im at a loss on what i can do to help her. I cant try to get fit, buy new clothes, or even shave my face without her thinking im seeing someone. Ive tried to tell her that 2 wrongs dont make a right and i wouldnt do that. she says she knows but i think in her mind she truly thinks somthings going on. I love her dearly, with all my heart and soul. I just want that girl i met in '99 to come back to me. Please help me if you can. My boys and I need her.