Pre-flop: (
8 players) Hero is Button with
UTG folds, UTG+1 calls,
3 folds,
Hero raises, SB calls, BB calls, UTG+1 calls.
Flop:

(
8SB, 4 players)

SB checks, BB checks,
UTG+1 bets, Hero calls, SB folds, BB calls.
Turn: 
(
5.5BB, 3 players)

BB checks,
UTG+1 bets, Hero ?
I should have raised the flop. He could easily have been betting into a draw. However, how do I avoid compounding that mistake on the turn?