Help me figure out why I apparently suck at 5/10 6max pt. 5: AKs IP

[Dex]

CO wasn't particularly aggressive, but didn't seem to be a complete fish either.

Party Poker 5/10 Hold'em (6 max, 6 handed) converter

Preflop: Hero is Button with A[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/club.gif[/img].
<font color="#666666">1 fold</font>, MP calls, <font color="#CC3333">CO raises</font>, <font color="#CC3333">Hero 3-bets</font>, <font color="#666666">2 folds</font>, MP calls, CO calls.

Flop: (10.40 SB) 2[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/club.gif[/img], Q[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(3 players)</font>
MP checks, CO checks, <font color="#CC3333">Hero bets</font>, MP folds, CO calls.

Turn: (6.20 BB) 3[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
CO checks, <font color="#CC3333">Hero bets</font>, CO calls.

River: (8.20 BB) 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">CO bets</font>, Hero ... ?