Is a psychiatrist recommending that? Or your family doc?
SSRIs (prozac, lexapro, effexor, celexa, zoloft and the like) are really not good for BP. They tend to bring on mania. Especially if not taken with a mood stabilizer!!!!!
Yes, they have sexual side effects, desire, performance and ability to orgasm are very common problems that don't go away unless you stop the medication. Weight gain can happen, not always.
If you aren't on a mood stabilizer, you need to be - and one of the best antidepressants for BP is Lamictal. It's actually not an antidepressant, but it works very well for BP depression. Sometimes they prescribe Welbutrin with it, a good combination. Neither of these have weight gain or sexual side effects.
If you're not seeing a psychiatrist, you really ought to. They know myriads more than GPs.