Did I Cost Myself a Big Bet

[Pedigree]

MP2 is ultra-aggressive. He bets hard when he has a great hand, a marginal hand, or nothing (on a bluff). MP3 and CO are both horrible calling stations that just call and call and call (CO is particularly bad). No read on BB.

Party Poker 2/4 Hold'em (10 handed) converter

Preflop: Hero is MP1 with Q[img]/images/graemlins/spade.gif[/img], Q[img]/images/graemlins/heart.gif[/img].
<font color="#666666">3 folds</font>, <font color="#CC3333">Hero raises</font>, <font color="#CC3333">MP2 3-bets</font>, MP3 calls, CO calls, <font color="#666666">2 folds</font>, BB calls, <font color="#CC3333">Hero caps</font>, MP2 calls, MP3 calls, CO calls, BB calls.

Flop: (20.50 SB) 3[img]/images/graemlins/heart.gif[/img], J[img]/images/graemlins/heart.gif[/img], 2[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(5 players)</font>
BB checks, <font color="#CC3333">Hero bets</font>, MP2 calls, MP3 calls, CO calls, BB calls.

Turn: (12.75 BB) J[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(5 players)</font>
BB checks, <font color="#CC3333">Hero bets</font>, <font color="#CC3333">MP2 raises</font>, MP3 calls, CO folds, BB folds, Hero calls.

River: (18.75 BB) 5[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(3 players)</font>
Hero checks, <font color="#CC3333">MP2 bets</font>, MP3 calls, Hero calls.

Final Pot: 21.75 BB

Because there were four other players on the turn should I have just assumed that somebody had a J and checked/called the turn and the river? Or would you check/fold (I think the pot is too big to justify doing that)?

In the end I only cost myself 1 BB because I assumed I was beaten when raised.