Finding a new therapist won't stop the issue, You'll just startr feeling the same thing for the new therapist. Don't avoid. Bring it up, this is normal to feel jealous. I don't see why it would be inappropriate, unless you two are having a relationship that is more than T/client. Transference is normal and a good sign in therapy.

I know it sucks but you just need to bring it up again with him and tell him so he can put your mind at ease. Do you know where this is stemming from? I mean this huge fear of rejection you have towards someone like him?