Button is very lag 38/21, (but seems like a pretty good player from what I've seen from him)so he could have any two raising on the button. I have been playing Tag and haven't gotten out of line. I think his most likely hand is a pocket pair or maybe some crappy straight draw when he checks behind on the turn, and so I think he cannot call a push on the river. Thoughts?

PokerStars No-Limit Hold'em, $4 BB (6 handed) Hand History Converter Tool from FlopTurnRiver.com (Format: FlopTurnRiver)

BB ($200)
UTG ($400)
MP ($488.10)
CO ($148)
Button ($1362.15)
Hero ($396)

Preflop: Hero is SB with J, A.
3 folds, Button raises to $12, Hero raises to $48, 1 fold, Button calls $36.

Flop: ($100) 8, 5, 3 (2 players)
Hero bets $68, Button calls $68.

Turn: ($236) 3 (2 players)
Hero checks, Button checks.

River: ($236) 5 (2 players)
Hero bets $280 (All-In)