Sleep Issues

Owen has always been a pretty good sleeper. He's slept consistently through the night since 4 months old. However, recently he's decided that he needs to cry at night sometimes up to 6 times a night. Michael and I are going with the tough love approach and letting him crying it out. The most it's taken him to get back to sleep has been 8 minutes of crying so it's not too bad. The thing I don't understand is what changed...he was sleeping 11 hours every night just fine and all of the sudden this habit started. I read online that he's at the age now where he's going through separation anxiety and he remembers us when he wakes up and he wants to be social at all hours of the night so maybe that's what's going on. All I know is I'm not going to start a bad habit like feeding him again in the middle of the night that will only have to be broken later. Any suggestion would be greatly appreciated.