A Poorly played JJ

[LA_Price]

Party Poker No-Limit Hold'em, $1 BB (9 handed)
loose passive table. This is my second orbit.

Hero ($45.50)
SB ($49)
BB ($65.55)
UTG ($48.90)
UTG+1 ($87.12)
MP1 ($39.10)
MP2 ($42)
MP3 ($89.50)
CO ($353.72)

Preflop: Hero is Button with J[img]/images/graemlins/spade.gif[/img], J[img]/images/graemlins/heart.gif[/img].
UTG calls $1, UTG+1 calls $1, MP1 folds, MP2 folds, MP3 calls $1, CO calls $1, <font color="CC3333">Hero raises to $4</font>, SB folds, BB calls $3, UTG calls $3, UTG+1 calls $3, MP3 calls $3, CO calls $3.

Flop: ($24.50) 7[img]/images/graemlins/spade.gif[/img], 9[img]/images/graemlins/spade.gif[/img], 6[img]/images/graemlins/spade.gif[/img] <font color="blue">(6 players) </font>
BB checks, UTG checks, UTG+1 checks, MP3 checks, CO checks, <font color="CC3333">Hero bets $15</font>, BB folds, UTG folds, UTG+1 calls $15, MP3 calls $15, CO folds.

I think this was my main mistake. Should I have overbet the pot or just moved in here? My thought was I should have moved in because if I overbet i'd only have a few dollars left anyway.

Turn: ($69.50) 2[img]/images/graemlins/spade.gif[/img] <font color="blue">(3 players) </font>
UTG+1 checks, MP3 checks, Hero checks.

River: ($69.50) 4[img]/images/graemlins/heart.gif[/img] <font color="blue">(3 players) </font>
<font color="CC3333">UTG+1 bets $20</font>, MP3 folds, Hero folds.

Final Pot: $89.50
<font color="#990066">Main Pot: $69.50, won by UTG+1.</font>
<font color="#990066">Pot 2: $20, overbet by UTG+1.</font>

I hadn't seen UTG+1 make any moves yet so I was confident he had me beat. His final bet just looks like it want's to get call so he probably has the ace, k, or Q. Any thoughts or comments or other ways in which i played this hand poorly?