JJ against 4 low straight cards and loose player

$.10/.25 NL 6-max

Villain has not been at the table long but I do know that he is pretty loose and does a lot of calling.

Hero $41
MP $57
CO $29
Button $23
SB $27
BB $15

Hero is UTG with J [img]/images/graemlins/club.gif[/img]J [img]/images/graemlins/heart.gif[/img]

Hero raises to $1, MP calls $1, CO calls $1, Button calls $1, SB folds, BB folds.

Flop (Pot $4.35): 5 [img]/images/graemlins/spade.gif[/img]4 [img]/images/graemlins/heart.gif[/img]6 [img]/images/graemlins/heart.gif[/img]
Hero bets $4, MP folds, CO calls $4, Button folds.

Turn (Pot $12.35): 3 [img]/images/graemlins/club.gif[/img]
Hero?

I honestly have no idea what Villain holds. Obviously I am most afraid of him holding a 7. I don't think he has an overpair higher than mine since he never raised, and I'm sure he would use his loose image to his benefit after I showed strength. Two small pair is unlikey in my mind as well, as he doesn't seem wild enough to call preflop raises with those types of hands. If a non-straight undercard or a 2 comes here, I feel safe making a pot-sized bet, but he called my flop bet with something. I apologize if this is elementary but I truly have no idea what the correct play is here against a loose player on whom I have no read.