I've been where you are. Lost a relationship with someone I cared very deeply for. But using a strategy I was able to get my ex back.
And you can get yours back too. But you need a strategy to get your ex back that will also help you determine if you even want them back.
But before you go on your mission you need to assess where you went wrong to cause the breakup. This is not to lay blame at anyone's feet it's just that the only person you can change is your self. You can't change other people.
Were there things about your ex that in hindsight seemed rather petty to complain or breakupabout? If yes a strategy for determining whether something is worth fighting about is to first determine whether or not something has:
positive effect
negative effect
no effect at all.
If it's a positive effect encourage the person to keep doign what their doing.
If it's a negative effect, take immediate action to end it. But do this while involving the other person as you can't make decisions that effect other people without allowing them input. And they might not know what they're doing is causing problems.
If it has no effect at all leave it alone. It's simply not worth squandering your energy or other people's goodwill by making everything a crusade.
On the other hand if it was the other person that was constantly complaining over petty stuff you might not want them back.
And finally if the relationship ended because the other person was abusive in anyway, count your blessings that it's over. Love without respect and the tender loving touch is not worth it.