PokerStars No-Limit Hold'em, $2 BB (6 handed)

CO ($52.80)
Button ($281.85)
SB ($35.20)
BB ($600.70)
Hero ($296.20)
MP ($406.30)

I had no reads on my opponents.

Preflop: Hero is UTG with A, K.
Hero raises to $7, MP calls $7, CO calls $7, Button calls $7, 2 folds.

3 callers = bad result

Flop: ($31) 3, 8, K (4 players)
Hero bets $23, MP calls $23, CO folds, Button folds.

nice flop: what about the bet size?

Turn: ($77) 8 (2 players)
Hero checks, MP bets $50, Hero calls $50.

correct play?

River: ($177) 7 (2 players)
Hero checks, MP checks.

Final Pot: $177

Your comments?