ProTools for the last 20 years

What it sounds like is you need to cut down on reflections. This means  treating the hard flat reflective surfaces with something that has absorption/deadening potential. You could definitely go low budget with household items. Blankets and pillows can work. Or you can go to a more permanent route with the Auralex type foam or QR diffusers to scatter the reflections. As stated already in the comments, you want to treat the back wall first, as that is going to be the source of most of your audible reflections. Second would be your side wall reflections. Cheers!