Flopped flush against TA-N, am i throwing money around?

[lightw1thoutheat]

Hey,
this just happened to me tonight, and I'm wondering if and when i should give the him credit for the nuts.
Button is 15/6 over 250 hands with aggro factor 1.63 without preflop included.

Party Poker 2/4 Hold'em (9 handed) converter

Preflop: Hero is BB with J[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/diamond.gif[/img].
UTG folds, UTG+1 folds, MP1 folds, MP2 calls, MP3 folds, CO calls, Button calls, SB folds, Hero checks.

Flop: (4.50 SB) 5[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
Hero checks, MP2 checks, CO checks, <font color="#CC3333">Button bets</font>, <font color="#CC3333">Hero raises</font>, MP2 folds, CO folds, <font color="#CC3333">Button 3-bets</font>, <font color="#CC3333">Hero caps</font>, Button calls.

Turn: (6.25 BB) 3[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">Button raises</font>, <font color="#CC3333">Hero 3-bets</font>, Button calls.

River: (12.25 BB) T[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">Button raises</font>, <font color="#CC3333">Hero 3-bets</font>...??

Is this a bad play? (Second nuts aren't always good)
I really liked the three bet when i did it, but i cant imagine what kind of hands he'd be playing that i can beat. Advice please.