This pain is so unbearable. I broke up with my boyfriend and I regret it something awful.
Sounds like you're miserable without him, but if you broke up with him why do you regret it now?
I  didn't realize how much I loved him until it was too late.
Sometimes it's hard to realize how good something is when we have it. You can always try to make amends with your ex. If you let him know how you feel, you may rekindle the relationship.
I'll try.
I'm excited that you're willing to give this a try. At least you can say you were honest with him not matter what happens.