A therapist friend of mine said that a good therapist will help you let through as much emotion as you can deal with at any given time. So I think it's a good thing you've got a date with one. You sound completely overwhelmed, and while I understand the not wanting to leave the house (you feel out of control, you want to be in control), I'm glad you have plans to talk to someone.
I found that a therapist helped me sort things through, put them in "boxes" in my mind, decide which boxes to deal with NOW and which boxes I could put in storage, so to speak. I think most of all, she gave me permission to NOT feel functional all the time; to take days when I stayed in bed and watched Netflix all day.
(((hugs)))