[Milo]

Actual, real-life clinical psychologist here. Gina's posts were essentially correct. Other antidepressants, even other SSRIs may have a lesser effect. Loss of libido, difficulty sustaining erection or difficulty having an orgasm are all very common side effects of many antidepressants. For most, the sexual side effects are not as bad as the depression, but this certainly should be explored further with your psychiatrist, and please see a psychiatrist rather than a PCP. There may be other med options that will effectively treat your depression, but allow a greater degree of sexual functioning.

And I'd recommend printing out info for your GF, to help her understand the sexual problems you are having. Depending on the seriousness of the relationship, consider bringing her along to a counseling session or two (assuming you are also in therapy). Sexual problems have a way of becoming bigger over time, and overlapping into other areas, so they should be addressed. Some people in your situation begin avoiding sex, which only makes the relationship problem worse.