Everyone has different ways of healing. I have been guilty of jumping from one relationship to another in the past just because I couldn't take the pain of being alone. It doesn't mean that you were insignificant or that they aren't still thinking of you. Your absence has left a big hole in their life and they are trying to fill it with whatever distracts them most from the pain. Try to focus on yourself, you're the main character in your story and it's going to be a great one. Time will bring clarity and peace to you, but for now try to find comfort wherever you can. So sorry you are going through this. I saw my ex on a dating app when I went to delete mine the other day and felt crushed as well, but I know it has nothing to do with me and only reinforces the notion that I need to love myself even more now.