nl100 rivered bottom set, gotta fold here, right?

[Brimstead]

no real reads on villain, 21/5/1.5 after 20 hands

Poker Stars, $0.50/$1 NL Hold'em Cash Game, 9 Players
LeggoPoker.com - Hand History Converter

MP2: $37.35
CO: $104.90
BTN: $98
SB: $378.60
BB: $44.50
UTG: $61.95
UTG+1: $26.25
Hero (UTG+2): $100.45
MP1: $99

Pre-Flop: 2[img]/images/graemlins/heart.gif[/img] 2[img]/images/graemlins/diamond.gif[/img] dealt to Hero (UTG+2)
2 folds, <font color="red">Hero raises to $4</font>, 3 folds, BTN calls $4, 2 folds

Flop: ($9.50) A[img]/images/graemlins/diamond.gif[/img] 8[img]/images/graemlins/spade.gif[/img] 5[img]/images/graemlins/diamond.gif[/img] (2 Players)
<font color="red">Hero bets $5</font>, BTN calls $5

Turn: ($19.50) J[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $13</font>, BTN calls $13

River: ($45.50) 2[img]/images/graemlins/spade.gif[/img] (2 Players)
<font color="red">Hero bets $23</font>, <font color="red">BTN raises to $76 and is All-In</font>, Hero ?

i know flop is bad, my cbet was too small. i probably should have check/folded the turn, but i took a shot anyway in the hope he might fold a marginal hand.
I can't think what i beat that he's raising with on the river, apart from a busted draw. would AJ wait until the river to raise? i think a set or backdoor flush are his likely holdings here. Is this a fold? would a check/call on the river been a better move?

thanks in advance for comments [img]/images/graemlins/smile.gif[/img]