"I don't want to hurt him" you couldn't possibly hurt him. Only the ego feels pain.
If for example me and you were in a marriage for that long and we got a divorce I would have no problem with you dating someone new. I would actually encourage you to find someone that would make you truly happy.
His own ego and insecurities would cause him to feel hurt by your new relationship. The problem lies with him, not you.
It becomes a problem when his jealousy/insecurities start interfering with your happiness (moving on and finding someone new). At that point you need to make a choice of whether or not it's healthy to keep your ex husband around.
I suggest putting a lot of space between you and your ex husband. It will give him time to get his issues in order and time for you to release some of the guilt you have been holding onto.