You need to work with therapist but as a short term solution try to substitute something else for calling him. Call your girlfriend? Sister? Go to gym? Clean? Go to public place where you can’t call? Post on here? Be too busy to call until you are over it.

I once told my t that j am not doing something (not related to relationships) because it causes me anxiety. She asked “you know being anxious not going to kill you, do you?”. I’ve been doing it since then despite being anxious because she was right. I survive.

You’ll shake today and tomorrow but a week from now you won’t shake.