Trying to fold an overpair

Live 30/60 game, 6 handed at the moment. I should have a good image. Folded to a TAG CO, who I'd say plays in a typical 2+2 style, who raises. Button folds, too loose SB calls, I call with T [img]/images/graemlins/club.gif[/img] 9 [img]/images/graemlins/club.gif[/img]
Flop comes down 4 [img]/images/graemlins/spade.gif[/img] 7 [img]/images/graemlins/club.gif[/img] T [img]/images/graemlins/diamond.gif[/img]

SB checks, I check, CO bets, SB calls, I raise. CO 3bets reasonably quickly. SB rechecks his cards and folds, I call.

Turn is 8 [img]/images/graemlins/club.gif[/img]
I donk, he raises quickly again, I 3bet in tempo, he pauses for a minute, looks at me quizzically, and calls.

River is 3 [img]/images/graemlins/spade.gif[/img]
I check with the intent of folding to a bet.

Questions:
Am I just spewing on the turn?
Is it worth the bet on the river?