Have you discussed this with your T yet? I think that you need to talk about what is being triggered up from the past with your T and let all of those feelings out in session. Once you release some of the pressure from that end, while you are in class you need to make the connections that this prof is triggering up your old issues, and tell yourself that this prof is not your mom. Once you can diffuse the past trigger and then stop that automatic connection/trigger in the present, you should start seeing some relief.