sorry that your previous post got hijacked. Can completely understand you starting a new, fresh one.
Yes, you can ask. But you may not get an honest answer. My own approach would be to simply figure out if his behaviour was what I want in a partner. If it's not, then just move on.
One positive: if you do decide to move on from a person who's not bothering with you, at least you don't have to have an awkward discussion about it. You just stop contacting them.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.