I have been on Wellbutrin XR 300mg for 2 years. It worked well for me on my severe crying spells. It definitely decreased my libido (although that was already an issue due to my major depressive disorder). I would definitely recommend going up to 300mg. I didnt have any crazy side effects on this dosage.
Not to diminish nurse practitioners, but they aren't the best informed people out there. They have very little training and pretty much none in psychology. All drugs can stop working. We in the suffering biz call it pooping out. Most of us have had it happen. When it does, sometimes what you need is a higher dose. Sometimes it just stops working and you need to try something else. Sometimes it's not the drug at all, you just have a bad day or week because no medication cures depression, they just make it less bothersome. Some people do get cured in therapy, but we don't know what causes depression yet and so we can't cure it with medication. Very few things in life are cured by medication -- mostly they just tamp down symptoms. And they can all stop working if we're unlucky and our bodies just get too used to it.