NL50, tricky spot with KK in 4bet pot, quite deep

[chillout85]

Party Poker No-Limit Hold'em, $0.50 BB (6 handed) Hand History converter Courtesy of PokerZion.com

SB ($83.52)
BB ($50)
Hero ($77.37)
MP ($39.96)
CO ($91.15)
Button ($19)

Preflop: Hero is UTG with K[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/heart.gif[/img].
<font color="red"> Hero raises to $2 </font> , <font color="Gray">1 fold</font>, <font color="Red">CO raises to $6.5</font>, <font color="Gray">3 folds</font>, <font color="Red">Hero raises to $21</font>, CO calls $14.50.

Flop: ($42.75) A[img]/images/graemlins/heart.gif[/img], 2[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/club.gif[/img] <font color="Blue">(2 players)</font>

Hero??

No reads or history with villain. I really had little clue what to do in this situation, I thought about shoving preflop but decided against it as I thought he'd probably only call with aces or (unlikely) the other 2 kings. Also since we're pretty deep I thought a raise to $77 from $6.50 was a bit unncessary. It seems to me now that the size of my 4bet has left me in this spot on the flop where any significant bet commits me. Does anyone have issues with the size of the reraise? In terms of assigning a range to villain I thought it could well include AK/AQ/QQ all of which would leave me in pretty bad shape on this flop. That said, I think check/folding now would be incredibly weak given the preflop action. So what are my options? I have about $56 remaining, do I make a small bet and then fold to any action? Check/call?? Shove?! None of these seem particularly appealing but the idea of check/folding here makes me sick. Comments on anything are welcomed