My heart goes out to you and all that you are dealing with. I pray all goes well with the management of the tumor. You are strong. Stay positive.
I teach that the way you dress is a reflection of how you feel. (If you look good you feel good). You mentioned that you do not wear most of your clothes in your closet, and the ones that you do have don't fit. Did you ever think of replacing some of the pieces that don't fit? If not, let's start there. Your wardrobe should bring joy and excitement... and the clothes should fit, lol.
Do this one piece at a time. No need to rush the process.
Also, I think it is great that you have a bra collection! Not every woman can say that.