Huh? Bet or no?

[Jimbobobb]

Party Poker 0.50/1 Hold'em (7 handed)

Preflop: Hero is UTG with 9[img]/images/graemlins/diamond.gif[/img], 9[img]/images/graemlins/spade.gif[/img].
Hero calls, MP1 calls, MP2 folds, CO calls, Button folds, <font color="CC3333">SB raises</font>, BB folds, Hero calls, MP1 calls, CO calls.

Flop: (9 SB) 6[img]/images/graemlins/club.gif[/img], 3[img]/images/graemlins/club.gif[/img], 6[img]/images/graemlins/diamond.gif[/img] <font color="blue">(4 players)</font>
SB checks, <font color="CC3333">Hero bets</font>, MP1 calls, CO calls, SB calls.

Turn: (6.50 BB) 7[img]/images/graemlins/heart.gif[/img] <font color="blue">(4 players)</font>
SB checks, <font color="CC3333">Hero bets</font>, MP1 calls, CO calls, <font color="CC3333">SB raises</font>, Hero calls, MP1 calls, CO calls.

River: (14.50 BB) 3[img]/images/graemlins/diamond.gif[/img] <font color="blue">(4 players)</font>
SB checks, Hero........

wha? ummm alright..... I don't know about betting this river. If I get c/raised I seriously might just throw up. There are also 2 other people in the hand, and maybe one has a 3 or a 6.....I think betting this river is ridiculous, and I don't know how to respond to a bet.....but I dunno. I was confused with this hand. Any and all comments welcome.

edit: I honestly don't have any real reads on these guys....SB is:

40% vpip
15% pfr

over 108 hands