getting pushed out on the river

hi, i've been lurking around the forums for about a month now. i'm learning everyday. you guys are great.

time for my first post and first hand. don't have that much of a read, but mp3 was tearing apart the table, playing alot of hands, raising about every 10th pf, post flop semi-aggressive. he seems to be on a very lucky day. anyways, here's the hand:

i think that one of my many leaks is getting pushed out at the river. here is a hand. please comment on the river, but also on the other streets.

PokerStars 0.10/0.20 Hold'em (9 handed) converter

Preflop: Hero is UTG+1 with 4[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/spade.gif[/img].
<font color="#666666">1 fold</font>, Hero calls, <font color="#666666">2 folds</font>, <font color="#CC3333">MP3 raises</font>, <font color="#666666">1 fold</font>, Button calls, <font color="#666666">1 fold</font>, BB calls, Hero calls.

Flop: (8.50 SB) A[img]/images/graemlins/club.gif[/img], A[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
BB checks, <font color="#CC3333">Hero bets</font>, MP3 calls, Button calls, BB folds.

Turn: (5.75 BB) 6[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(3 players)</font>
<font color="#CC3333">Hero bets</font>, MP3 calls, Button folds.

River: (7.75 BB) 3[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets</font>, <font color="#CC3333">MP3 raises</font>, Hero calls.

Final Pot: 11.75 BB

i normally would not have called here, but this time i tried to. what do you think?