Perhaps both of you still love each other. However, you have to make sure that he love you too. This relationship will success only if you both still want it. If you still doubt about it, it means you still need more time to understand about your feeling and your desire.

You should try to handle your doubt. Think honestly, because if you have doubt, it will destroy all of your effort. Understand your situation first; what make you still have a doubt? Then, try to handle it before you come back to him. If you decide to back to your ex, make sure that you have faith that you have a way to handle your doubt.