Pro Poker School

I check-called the flop because I thought I had the best hand and I didn't think raising would be a good idea. He bet the Pot on the river which I dont think he would do with an A so I call again, and then K on the river. Here I decide to throw out a defensive bet, because if he doesnt have an A I dont think he could raise, and he might fold a better 7. Any thought on how I could have played it better, or differntly?