Turning 2 low pairs

[Beck]

Been slaughtered lately, by people hitting 2 higher pairs than me, or the board pairing up, counterfeiting my lower pair. Not sure whether I play these hands correctly, fearing that I might slowplay too much.

Party Poker No-Limit Hold'em Tourney, Big Blind is t50 (5 handed) converter

UTG (t1610)
MP (t1690)
Button (t1790)
SB (t1975)
Hero (t935)

Preflop: Hero is BB with 7[img]/images/graemlins/diamond.gif[/img], 4[img]/images/graemlins/spade.gif[/img].
<font color="#666666">3 folds</font>, SB completes, Hero checks.

Flop: (t100) 7[img]/images/graemlins/heart.gif[/img], A[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets t50</font>, SB calls t50.

Turn: (t200) 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets t150</font>, SB calls t150.

River: (t500) 9[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>

Hero bets 275, SB raises all-in, hero is all-in

Final Pot: t500