How can I move on from this?
By taking one day at a time. It's very hard to move on from a great love but for your own sake you have to. Over time it gets easier, but that's cold comfort right now. Keep occupied, go out, socialise, do something that interests you, be it painting, carpentry, baking or amateur theatre, and maybe join a group where you can meet others who share your interests.
Block all contact with your ex. No peeking either, you'll only end up hurting yourself.
You're not alone, we've all been there, and it does get better. Take care of yourself.