When I broke up with my last boyfriend, I didn't feel any sadness. The time had come to go our seperate ways, it was never going to work. I was moving on to something new, something exciting so why should I have felt sadness? We had a great time, for the most part, but the time came where we just had to move on. To me, it was a sense of relief and it didn't upset me in the slightest. People take break up's differently, for example my ex insulted me constantly, he harassed me for months. Look at the difference between us both, we came from the same relationship.
It's possible that it was just time for you to move on, you don't have to be sad that you are moving on because you'll experience lots of new, exiting, different things. Maybe it was just such a relief that it feels like it's a weight off your shoulders? Nothing wrong with that.
It's possible that you'll feel sadness when the break up finally hits you. Despite it happening, sometimes things don't really register for a little while and when it does, you'll feel the way you think you should be feeling. There is no way that you should be feeling, it's different for everyone so if you don't feel upset, you don't feel upset. There is absolutely nothing wrong with that, you'll deal with it in your own way.
Feeling the way you do, it seems like you did the right thing. Don't feel bad about doing the right thing, be glad you did it and move on.