Thoughts on my play here?

PokerStars No-Limit Hold'em, $0.25 BB (5 handed) from (Format: FlopTurnRiver)

BB ($13.20)
UTG ($29.05)
MP ($18.10)
Button ($33.30)
Hero ($32.55)

Preflop: Hero is SB with 7, 7.
UTG raises to $1, 1 fold, Button calls $1, Hero calls $0.90, 1 fold.

Flop: ($3.25) 5, 9, 7 (3 players)
Hero bets $2.5, UTG raises to $6, Button folds, Hero calls $3.50.

Turn: ($15.25) 9 (2 players)
Hero bets $6.75, UTG calls $6.75.

River: ($28.75) 3 (2 players)
Hero bets $16

Flop
That's a slight underbet but OK. When he raises you I would like a 3-bet here, he's repping an overpair (which he may or may not have) and will probably committ himself.

Turn
That's a bad card for you unless he has a 9, it allows him to get away from an overpair since your betting on the flop repped a 9. Your bet is way too small. If you want to win a big pot you have to builda big pot. I would bet 2/3 of the pot at least, you're betting less than half.

River
If your bet sizes had been a bit bigger previously this would be an easy all-in. Still, if he has an overpair he probably can't fold it by now so you could try a push.

Would there ever be a point in a cash game you would worry? What if the opponent and I were x3 buyins deep?