Hi Peter86. I think working on this issue with a therapist and joining a support group may be helpful. Also, I learned that a triple-column journaling is helpful in sorting out your feelings. Please see the following link.

CBT Technique: Using the Triple Column Technique to Change Your Thoughts To Change Your Life! | Psychoeducation in Psychotherapy

And your idea about joining social clubs and activities are also great! Finally, knowing that what you are feeling is a natural reaction to what you have gone through, may help you to feel less stressed about it. I also struggle with trusting people after I trusted them and the outcome was not so good. But we need to take one day at a time, since overcoming these issues cannot happen overnight.

Thanks for posting! I think your experience resonates with some people.