flopped overpair OOP...

[sweet wicking action]

Party Poker 2/4 Hold'em (10 handed) converter
The player UTG has been playing very loose passive, something along the lines of 50/1/.5. MP3 has been fairly solid, and the Button is new to the table, this is his first orbit, and I have no reads on him.

Preflop: Hero is BB with 9[img]/images/graemlins/club.gif[/img], 9[img]/images/graemlins/heart.gif[/img].
UTG calls, <font color="#666666">3 folds</font>, MP2 calls, <font color="#CC3333">MP3 raises</font>, <font color="#666666">1 fold</font>, <font color="#CC3333">Button 3-bets</font>, <font color="#666666">1 fold</font>, Hero calls, UTG calls, MP2 calls, MP3 calls.

My initial feeling was that I should fold this hand, but then, I like to see flops, cause I've got no discipline. How is my line from here on?

Flop: (15.50 SB) 6[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/heart.gif[/img], 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(5 players)</font>
Hero checks, UTG checks, MP2 checks, <font color="#CC3333">MP3 bets</font>, Button folds, <font color="#CC3333">Hero raises</font>, UTG calls, MP2 folds, MP3 calls.

Turn: (10.75 BB) 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, UTG calls, MP3 calls.

River: (13.75 BB) 6[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, UTG calls, MP3 folds.

Final Pot: 15.75 BB