King Diamonds, to check or not to check (100NL @ UB)

[SharkSandwich]

Even back in my SSL posting days I always found it nearly impossible to find a hand of mine I had doubts over, after the fact. This one might be standard, but to me (a new NL player) in toto, it leaves me with questions.

Villain is a 24/6/1.3 Tag. And sadly my attention was mostly on another table. My image, I'm a buyin down, haven't won a significant hand, and lost a few small/mid pots at showdown.

We've been involved in one significant hand.

Where he openraised ($3.50), had a caller, and I 3-bet to $17 with QQ from BB. They both called.
Flop comes AJ9r. He calls my 28 bet into the 50 pot. And I check-fold to a 50 bet when a second Jack hits the Turn.

Ultimate Bet No-Limit Hold'em, $1 BB (5 handed)
Hand History Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

SB ($113)
BB ($344.90)
UTG ($96.50)
MP ($89.75)
Hero ($105.30)

Preflop: Hero is Button with K[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">2 folds</font>, <font color="#CC3333">Hero raises to $3.5</font>, <font color="#666666">1 fold</font>, BB calls $2.50.

Flop: ($7.50) 6[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, <font color="#CC3333">Hero bets $6</font>, BB calls $6.

Turn: ($19.50) 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
BB checks, Hero ?...

If we bet the Turn and get Checkraised pot (which leaves us with a 1/3 of our stack if we call) are we committed to getting the rest in behind, and praying for a diamond?

If we check, we call a river bet,
But if we're Checked to we?...

Thanks for any replies.