Let me applaud you for doing the right thing. You were honest. The problem with the right thing is that it's not particularly sexy. No one throws parades for telling the unadorned truth.
It sucks. There's a reason doing the wrong thing is so attractive. It's easy. You get to tell people what they want to hear, while getting what you want. The truth is naked and it shakes in the cold. Lies dress to kill.
If you don't love the guy, you don't love him. You know what I can't stand about cowards? How they'll risk the feelings of people they know just to protect their own. You didn't do this. You broke his heart, and, in a way, yours too. It's never fun to be responsible for another persons suffering. But you don't always get to be the hero of your own little movie. Sometimes, you have to be the bad guy in some other persons movie. It sounds like you've taken responsibility for hurting this guy.
But it's not over quite yet. What do you do now? You grin and bear it. Take that pain you feel, and put it in a cooler deep buried deep within your guts. Your guilt does not trump his heartbreak. There is nothing worse than being dumped and then having to tend to the wounds of the person who dumped you. Do this guy a favor and move on. Fast. Replace your heart with that of a robot. Be cold. It'll make it easier for him to move on. And, look, no one gets over something like this quickly. But fake it, and eventually, you'll start acting like you've gotten over it. Eventually, you will get over it.
Go out with friends. Eat ice cream cones. Start making passes at cute guys at the park. The sooner you start living your life, the sooner the both of you can get on with life.