Not Sure I Should Go Back with Him

You have doubts about starting over because you're worried that he won't take your relationship seriously. Tell him just that! Describe exactly what he said and did (or didn't say and didn't do) the last time around.

He needs to be clear on what gave you the feeling that he wasn't taking your relationship seriously. Then ask him how you can be sure that he will behave differently this time around. Let him sell you. Let him tell you why he's so sure that he's different.

When you hear what he has to say, you'll be in a much better position to make a decision.

You also might decide to give the relationship a trial run. This way you can protect yourself by not jumping in with both feet until he demonstrates that he really is different.