Most Helpful Guy
Most Helpful Girl
It's because you're missing the fact that you had a boyfriend.
When the initiator of the breakup is sad, it's usually cause they miss the feeling, or that they're slowly starting to doubt that decision.
You make it clear that you don't miss him, so I'm going to assume that right now, you miss the happiness that came out of the relationship and the simple fact that you were with someone who used to give you fuzzy feelings.
Usually when people are in a relationship, they place their boyfriend \girlfriend on a higher priority scale, and they push away other thing overtime, like hobbies or friends. Reconnecting with friends and doing or re-discovering new hobbies will help.
Also, when you get the urge to cry or even think about your ex, do something else. And, I know you might not want to do this, but try dating again. This can boost your confidence.
Here's some things that I'd avoid for now: drinking, making rash decisions, jumping into new relationships too fast, and looking at things from your previous relationship. Put things like pictures of you two away, in a box either under your bed or in your closet, so you won't be easily reminded.
And finally, try meditation, and focus on how good it feels to be single. If your grief lasts persistently for six months or more, have suicidal thoughts or thoughts of self-harm, or feel like you can't function normally, seek help because those are signs of depression.
Don't worry, you'll feel better.
-Sincerely, a girl who broke up
with her first love about eight