Any reason to worry here?

[TheJunkyardGod]

Playing 2-4 at the Borgata this morning (I was low on cash and couldnt afford anything higher) I played this hand and was curious to get some opinions.

I'm in middle position with 66. Three people are in the hand so far and I call, with the button and the two blinds right behind.

The flop comes down 6-J-K rainbow, it's checked to me and I bet. Two people call.

Turn is another K, the first guy bets, second one calls and I raise. The first guy folds and the second simply calls.

The river is an Ace. The other guy bets, I raise only for him to reraise. I'm pretty confident he must have a straight and I raise again. Suprisingly, he 5-bets and after a second, i'm convinced I have the best hand and raise one more time. He finally just calls.