Maybe the first thing you should do is to identify what are the reasons you can't get over her. Are there anything remind you of her - songs, activities, objects? If there are, you should confront them and dissociate them from her.
Finding new hobby or making yourself may work, but that's just you running away from your main problem. It's like you cut down a plant, but you leave its roots remain in the soil. Then, what happens? The plant grows back. In your case, your problem/feeling piles up and stops you from moving on.
This might be one reason why you're feeling empty - you have an unmet need. The emptiness you feel is a signal from your mind which urges you to meet the need.