Well what is your workout routine? If you workout in a gym do you only use BB? I see a lot of people in the gym doing the same thing day after day. Your muscle need to be tricked, shocked. Use everything 1 chest day use BB, next use DB's, next use machines, yes I said the machines lol they build little muscle that BB can't, making you stronger.
Maybe switch to the TUT program for a few months. I did that and my strength ended up going up big time. I don't care about strength anymore but it did go up.
Theres many many other ways but the first thing off the top of my head. If you are doing all these things just scream and well figure something else out.