You've got sound waves bouncing all over the place - off the walls, ceiling, floor, and furniture. In other words, your room is behaving like a reverb chamber because of the hard surfaces. You could spend a small fortune to professionally sound proof the room (which you would probably rather not do), or you could identify and dampen the offending surfaces using blankets, rugs, carpeting, foam rubber, or anything else that would cover a large area and absorb some of the sound. It's not gonna look pretty, but it'll significantly cut down the reflections. Also, you could build a blanket booth - a framework big enough for you to play your violin in, and cover it with heavy blankets. These are probably your only low cost options.