I am deeply sorry for the tragic loss of your beloved ds.
You've been given such a heavy cross to bear and I'm also extremely sorry that you are having to bear it's weight alone.
Your life has changed immeasurably and it's entirely natural that you feel unable to take pleasure in those things you once enjoyed doing, and that it would somehow be wrong for you to do so.
There's not much point in me saying 'be kind to yourself', honey, because at the present time your grief is such that you don't feel deserving of any reward, but I hope you can take some comfort from knowing that, while time will not heal, in time you will reach a point where you will begin to look outward again, albeit fleetingly at first.
You are going to be severely put to the test in a few weeks' time and it's inevitable that you will feel distraught until your youngest ds returns home safely for weekends and/or vacations.
It's imperative that you put some coping mechanisms in place to get you through what will be another harrowing ordeal made worse by fear of history repeating itself, and I would suggest that you seek more counselling as a matter of urgency and ask your GP to prescribe whatever is necessary to alleviate some small portion of your pain.
Have you posted on the Bereavement board which is in the Body and Soul section of this site? You'll find many there who have suffered, and are suffering, the enormity of losing a child and I hope they may be able to provide the comfort and reassurance you so desperately need to get you through the coming months.