Interferon/Ribovirin treatment

I have been on the treatment for  6 months now and have in the last two months started getting waves of depression a few times each day that last for approx 5-30 minutes the week before my period this worsens with and I start to fixate on different methods of suicide the actual week of my period it seems every second thought is suicidal and I spend a few days of hell coming up with the reasons not to do it.  I have never had problems like this prior to starting this treatment.  

My doctor put me on 20mg Ciparmil which seems to have been of no use so I stopped taking it.  Has anyone else on this treatment had any similar side effects and if so what was the best treatment.

My last blood tests showed no HepC and so I really want to complete the treatment but may have to stop treatment if this obsession with suicide continues because I feel that if the HepC doesn't kill me the potential cure will.