I have the same issue on Lexapro. Of course, depression itself annihilated my sex drive, too, so if I have to be without a libido I at least want to not be depressed!
Different antidepressants are prescribed for different symptoms...and some work well for some people but not for others. Some have a strong anti-anxiety component or are more compatible with other meds, so merely substituting Wellbutrin for Paxil may not be the answer. If Paxil works really great for you, then that's an important factor in deciding what to take.
The best thing for my libido has been regular exercise. Losing a tiny bit of weight and feeling strong and active -- it's really improved my self-image and made me feel more desirable, which helped overall. I still don't have a huge desire and the "o" is hard to get to, but exercise has definitely helped (and of course I'd never have gotten to the point of feeling like exercising if I hadn't been on Lexapro for over a year).