desperation bet on the river, blind play

Villain is 44/0/0 over 25 hands

Party Poker 3/6 (6max, 6handed)

Preflop: Hero is BB with 8[img]/images/graemlins/heart.gif[/img], 4[img]/images/graemlins/diamond.gif[/img].
2 folds, CO calls, 2 folds, Hero checks.

Flop: Q[img]/images/graemlins/heart.gif[/img] 7[img]/images/graemlins/heart.gif[/img] 2[img]/images/graemlins/spade.gif[/img]
Hero checks, CO checks.

Turn: K[img]/images/graemlins/heart.gif[/img]
Hero bets, CO calls.

River: 5[img]/images/graemlins/club.gif[/img]
Hero bets...

all postflop streets very debatable IMO.