+1, your efforts to save money by doing your own work is costing you dough. When you have chronic problems that others don't have, it's time for a second opinion, preferably from an expert who has it in his hands, rather than from a forum where people don't and have to speculate.

In your shoes, I ask around and track down the local mechanic with a reputation for solving problems (not someone who just keeps replacing parts). You'll know you're on the right track when he gives you an explanation of the actual problem, and fixes it without replacing the BB, or shows you a field stripped BB indicating the exact damage that warranted replacement.