It sounds like you've been doing a pretty decent Bodybuilder's routine. If that hasn't been working for you, I would recommend trying a strength training routine, specifically Madcow's 5x5 program. There are a ton of stickys in this forum over it.
I had the same problem, and out of desperation, I finally made the switch. Afterwards, size and strength seemed to start flying at me from nowhere.
Whatever you do, good luck bro.