This hand is haunting me

[burningyen]

$2/4 NLHE at Mandalay yesterday:

Pre-flop everyone folds to me in late position. I limp with 56s. The rest fold to the BB, who checks. Up to now he has been playing quietly, seldom raising and folding to every raise.

Flop comes J85 rainbow. BB checks, I bet $15, BB calls quickly. Turn is 6 rainbow. BB checks, I bet $50, BB calls quickly again. River is another 6. BB bets $50. What should I have done?