too thin a value bet?

30/60 party, 10 handed

hero has QQ on the button, utg is a complete unknown


utg open raises, hero 3 bets, blinds call....

flop is JJ5 rainbow, check, check, utg bets, I raise, 2 folds, utg calls...

turn is a 9, utg checks, hero bets, utg calls

river is an 8, utg checks....

I have a strong feeling that I am ahead here, but here is my question.... what hand calls me down here that I can beat?, any J beats me, AA or KK beats me (remember, this is an unknown, so I have no idea how passive/agressive he is post flop), and now 99 or 88 beat me, so what possible hands that he would open raise utg preflop would he calldown w/ that I would beat?... am I overanalyzing and giving this guy too much credit??.... all I see myself beating is TT if he calls