Severly overplayed flopped flush?

[Brom]

Live 10/20 game that is extremely loose at the moment. There are typically 6-9 players to each flop for 1-2 bets each time.

I am in the big blind with 7[img]/images/graemlins/club.gif[/img]5[img]/images/graemlins/club.gif[/img]. 7 limpers, small blind completes and I check. So 9 players see for the flop for a pot of 9 small bets.

Flop is 4[img]/images/graemlins/club.gif[/img]6[img]/images/graemlins/club.gif[/img]K[img]/images/graemlins/club.gif[/img].
Checked around to MP who bets it, 2 callers in LP, SB calls, I raise, EP cold calls, everyone else who has a bet in calls, but this time around SB 3 bets, everyone calls except for one of the LP players.

So 5 players see the turn with a pot size of 13 big bets.

Turn is a brick, I don't remember the exact card, but I'm going to say it was the 10[img]/images/graemlins/heart.gif[/img].
SB bets out, I raise, EP player cold calls, the original flop bettor in MP cold calls, SB calls.

There are now 4 players staying to see the river in a pot that is 21 big bets.

River is a 2[img]/images/graemlins/diamond.gif[/img].

Sb checks, for some reason I bet, and all 3 other players call.

Originally my plan was to raise the turn to:
a) Prevent other people from raising it (unless they had the nut flush, I thought they wouldn't).
b) I was willing to call a raise, so I figured I'd do it myself and maybe fold a better flush (haha), or at least slow him down.
c) I was planning on taking a free river if possible (even though I didn't).

When SB checked the river again, I just couldn't resist betting. He was the only one I put on a flush, the others I put on two pair, set, and nut flush draw type hands. I had once seen the SB make this same play (call one bet then 3 bet when a bunch of players are trapped in) with a set, so there was the possibility he had a set again. It was not a monotone board the previous time he did it.

So there's the hand and some of my thinking behind it, lay into me.