In the hand, you are raising preflop, so the guy think you got Ax or KX, or pocket pair, or nothing, in the flop is no A or K, so the guy pay with 9's.
In the turn comes Q, now he got not only 9's, but also have a 2 ways straight draw (9,10,j,Q), so he check expecting to know where he was, but you check and give him a free card, and also make him feel you got nothing
if you raise in here maybe he trow the hand, or at least think that you got a hand, but because you check in the turn, he think that you dont have nothing.
In the river dont hit the straight, but a 7 come, so he think your hand is not better than before, so, he is going to pay.
Bluff is part of the game, but as you said have to be believable, and if you going to bluff, make it strong.
And bluffing or not, never give freecards in the turn.