BB special : 2 pair ... but facing river bet

Villian is uber LP/Fish. Saw him limp QQ on the button 3way few hands ago and lose to something. I'm really unsure of what hand range to put him on so this call was kind of painful. Does anybody fold here?

Party Poker No-Limit Hold'em, $ Hero (6 max, 6 handed) internettexasholdem.com

Hero ($60.95)
UTG ($11.70)
MP ($137.62)
CO ($46.50)
Button ($47.70)
SB ($52.50)

Preflop: Hero is BB with 7[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/diamond.gif[/img]. SB posts a blind of $0.25.
UTG calls $0.50, MP calls $0.50, <font color="#666666">2 folds</font>, SB (poster) completes, Hero checks.

Flop: ($2) A[img]/images/graemlins/heart.gif[/img], 3[img]/images/graemlins/club.gif[/img], K[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, Hero checks, UTG checks, MP checks.

Turn: ($2) 7[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(4 players)</font>
SB checks, <font color="#CC3333">Hero bets $1.9</font>, UTG folds, MP calls $1.90, SB folds.

River: ($5.80) 5[img]/images/graemlins/club.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $3</font>, <font color="#CC3333">MP raises to $15</font>, Hero calls $12.

Final Pot: $35.80