You are having adjustment related problems. It is very natural to feel that way. Uncertainties and fears make us brood and apprehensive creating self doubt. You must consult psychiatrist/psychologist for some supportive work. In case you have associated symptoms medicines can prove very helpful.

What you are experiencing is Adjustment disorder with anxiety and depression most likely. While giving it time may make it better it could take a long time.

Dear you, It would be best for you to get a therapist for yourself. Why 1. You will have one secure connection. 2. You will understand yourself 3. You have lot of unresolved issues and trauma. 4. You sound like a self aware human..therapy will be helpful 5. Before you get in New relation. Burn the old  once from your body. So there is fresh start. Be compassionate with yourself.. Imagine you want to plant a new tree. But the memory of old tree and how it failed and feeling of not being a good gardener.  So take help learn and plant. All the best.  Don't worry.  Things usually work out for people who want them to work out.

We are always there to help you.. book an appointment with any Psychiatrist to help you figure out the best for you