It really probably isnt the BB. The BB and cranks get blamed for anything. Change one thing at a time until you find it

1) Really tighten saddle / seatpost
2) Tighten down both QR
3) Swap out both wheels
4) Change out the chain
........

You will get it. I just got done with a pesky creak similar to yours. It just takes a little patience. Bike frames are efficient sound radiators, so you really cant hear where it is coming from.