Karen,
if that is your real name you might want to change it to protect your privacy and that of your adult children.
COM gave you good advice. I would only add...you don't need to take any action today. Find a support group. Post on the forum. Take steps towards leading your own, full, independent life. Work on spending a full day without thinking about your kids. Then see if you can make it two in a row.
About his stuff? Yes, I would probably move towards getting rid of it. How to do that I am not completely sure, but I do know that my own son left home at 17 (he is 21 now) and slowly but surely we have nothing in the house that is his anymore. He took some. We threw some out. We didn't accumulate anymore. At one point I told him that I was putting his drum set out on the curb in 2 hours, and he said he would be right over to get it...but he never came. He stopped to buy drugs and go to a party instead. I put them on the curb, and they were taken almost immediately by some one else, some one I hope uses them, or sells them or something.
I loved when my son played the drums, Karen. Music for him is his best and brightest self.
But he wasn't playing them anymore. Not in my house, not anywhere. The stuff in my house he wasn't using anymore.
Now his old room is a rather nice, simple, comfortably hang out room. And that is that.
You will feel better when his stuff is gone. How to get there is a process. Get help, as COM said. Take your time. It will all be OK.
Echo