You have to arrange with him when to meet to explain why you made that decision. It will be difficult for your boyfriend to accept your invitation because of the pain he is feeling as a result of your decision.
Call him. If he doesn't answer send him a text. Tell him it hurts you that you hurt him by making a rash decision. Let him know why you made the decision. Let him know what you were going through and how it affected the decision which you regret.
Let him know you love him. Ask for forgiveness and another chance. Let him know you are waiting for his response.
If he doesn't respond, wait a few days before you call or send him a final text asking for another chance. Again, let him know that you love him and you're patiently waiting for him. Don't beg again because you will only infuriate, annoy and hurt him the more.
If he doesn't want to get back with you, wait for more than a week before you try for the last time.
If things don't go well, it's time to accept the relationship is over. It's time to move on.