You can be happy without him. The first breakup always brings such thoughts.
The most important thing to remind yourself is that you have a future to live for. Your life isn't limited to the relationship.
Sometimes you'll find yourself thinking about your ex, and the thought life won't be good without him by your side. However, the feelings are a result of the emotional bonding that has been severed.
Think about people whose relationship had broken up, but they were able to sojourn on. They made it. You have to purpose to heal and recover from the breakup.
Whenever you find yourself thinking about him, tell yourself he is no longer yours. You'll need to think about other things than your ex.
You have to program your mind and tell your heart you have a life to live, and you can be happy irrespective of the breakup.
I suggest you read these articles:
1) Steps to Healing and Recovering from the Breakup
2) Things to Do and Not to Do After a Breakup
I wrote the above two articles with the intention of helping people to heal and recover from the breakup.
It's possible to be happy without your ex. Always remember that.