I wish I had a good answer. A mix of trusted friends and a thoughtful therapist. If you are in an abusive situation, a therapist should be able to identify it since there are objective frameworks to think about that. It's also easy to reject an "objective" diagnosis of a situation because you are likely to view it from your internalized perspective.
A strong hint is if you change the environment, and the problems suddenly disappear.
If the problems disappear slowly, it could have been the environment, but it also could be your personal growth. But if they disappear overnight...