Hi Arkansasnon,
I am sorry that you are going through this. I understand how it can be difficult to discern why your ex behaved in certain ways. The behavior can be baffling at times. It can be hard to understand how someone could put you so high on a pedestal and not want to talk to you anymore. It makes it more difficult when there is no closure. That type of pain is like a wound that never seems to close.
Working through the pain is difficult at times. Sometimes we can make it harder for ourselves by retrospectively looking back and thinking about the 'what ifs' and 'should haves.' I have done this myself and thought, "Maybe things would have been different if I validated him more or was more understanding." Usually I thought this after he projected, gave me the silent treatment, or raged at me. I would feel guilty that I could have done more to be supportive, understanding, or caring. He told me something that made me change my way of thinking. He said, "EaglesJuju, you would give me the world if you could, you would do anything for me and you continue to do so. It is never going to be enough. That is my problem and something that I am working on. I am like a black hole sucking everything out of you, something that never gets filled." He is right, no matter what I could have or should have done, it was/is not going to be enough until he works on himself in therapy and gets to a place of recovery. That is something that I cannot do for him. I cannot change the way he thinks or behaves.
When relationships end with no closure, it seems like we can be our own worst enemy. Self-esteem can plummet and self-doubt is very common. The aftermath of a relationship like this is similar to the Kubler-Ross' stages of grieving. Denial, anger, bargaining, and depression seem to vacillate in a cycle. These feelings are normal. Although they are normal, it does not mean that it is less painful.
Self-care is important while working through such difficult feelings. As you mentioned, therapy is great for that.

Think about those amazing changes and use positive self-talk whenever you are self-doubting. Sometimes our emotions can eclipse our logic. Mindfulness really helps giving another perspective by balancing our emotions and logic. When I am working through difficult emotions, I have had a tendency to let my emotions take over my logic. Practicing mindfulness and being in wise mind helps me feel centered. Take a look at this link.
TOOLS: DBT for Non Borderlines- Mindfulness No contact can be for many reasons. One is her simply not being interested. Others can be based on shame and avoidance, splitting etc. How was the no contact initiated?