Ever since I can remember my sex drive has been up and down like a yo yo as has this insatiable attraction to occassionally random (or not so random) men. I am 30 years old, and was with my husband for 12 years before I left him in October last year (after my diagnosis in September). I had been unfaithful in bursts over our entire time together. It is only now that I am starting to realise that whilst some of this was free will some of it was a symptom of the bi-polar when I had gone hypo-manic- I just couldn't control the urge. I'm now on Seroquel and Quetiapine and most of the time I'm OK although I do cycle about every 2-3 weeks.
Bi-polar is such a rollercoaster that we can't get off. The drugs just even out the bumps 
I've always had a higher sex drive than my husband (now I know it's partly because of bipolar). I was in a deep depression when I was diagnosed with bipolar 16 months ago. My sex drive was still there to some degree but I couldn't have an orgasm which was extremely frustrating. It disappeared a few weeks before being on meds. A year ago, I started experiencing the hypomanic sex desires even though I was still depressed. I couldn't get satiated but I still couldn't climax. When I switched therapists before I actually had a pdoc (my primary prescribed tegretol), I bemoaned that fact at one appointment and she did some research to find out that it's a common side effect of tegretol. I was so angry because all along I thought it was my fault...lowered my self esteem even lower...thought my husband was as frustrated as me even though he reassured me that he loved me no matter what. Here it was the medication. My pdoc confirmed that as a side effect when I started seeing him.
Once I was weaned off the tegretol and switched to lamictal, I've been able to occasionally have a full sexual experience. I still am working through the damage in my psyche of the self blame and get my head out of the way in order to fully experience lovemaking.
Since my husband has a lower sex drive...I've resorted to using a toy in between our times of making love. Takes care of the manic response of needing that release. I have never had a desire to be with anyone else than my husband...for that I am extremely thankful.