I'm 5'9", and I've been trying the pb and protein too. Good advice all around, in the past week since I've posted this up I'ved managed to put on almost 5 pounds. The problem is, I feel like it's mostly in my gut though. I cut cardio completely out, so maybe that factored into it too.
If you are not on a creatine product you might give that a try. The Phycological effects of putting on weight in a short amount of time can sometimes make a difference. It will give you that little bit of Hope you need. Else you might have Low Test. If that is the case, try novedex XT ( Test Booster ) it really works too, great product!!! Others on here will attest to it.