Flush draw

[Easystreet]

PokerStars 1/2 Hold'em (10 handed) converter

Preflop: Hero is SB with 8[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/diamond.gif[/img].
<font color="#666666">4 folds</font>, MP2 calls, <font color="#666666">1 fold</font>, CO calls, <font color="#666666">1 fold</font>, Hero completes, BB checks.

Flop: (4 SB) 9[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/diamond.gif[/img], Q[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(4 players)</font>
<font color="#CC3333">Hero bets</font>, BB folds, MP2 folds, <font color="#CC3333">CO raises</font>, Hero calls.

I semi bluff the flop with my flush draw, but then get raised by CO. He probably has top pair, but he is capable of raising here with a flush or straight draw himself. Would anyone 3 bet the flop?

Turn: (4 BB) 4[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets</font>, Hero calls.

Well villain did not take a free card, so that makes his flop raise less likely to be a semi bluff I think. If villain has top pair, I have picked up more outs to trips or two pair.

River: (6 BB) 3[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">CO bets</font>, Hero ????

Is it worth calling with my pair of fours?