I know you're feeling at a loss, but I would honestly love to have this 'problem'!
Best I ever get is when my son goes to scout camp for the weekend. I never have enough time to get everything done on the few days that he is not here (one weekend twice a year at most).
When he went last weekend I decided to relax rather than rush round doing things. So I dropped him off friday evening, went to the local pottery painting place and painted for 3 hours, next day I did some gardening in the morning, went to London to visit a friend and his daughter who I hadn't seen for 12 months, did some leisurely shopping on the way home, then had a lovely peaceful dinner in the garden with which I had a glass of wine (first one this year) and yes I did reflect on teh fact it would be nicer to be able to share the time with a partner but enjoyed it never the less.
Then I watched exactly what I wanted on the tv and went to bed without worrying about having to get up early. Sunday I had a lie in, went to visit another friend in the morning, did a few essential chores, mowed the grass before going to pick him up from scout camp at lunch time.
In all honesty I could really do with another weekend (or several) to myself sometime. Then I might get some of the chores done that I didn't get sorted this time, like filing paperwork, sorting out the photos that need to go into albums, emailing his grandparents in america, finish painting his bedroom that I started last summer, having some kind of social life so that I might be able to find myself that partner to share my peaceful meal inteh garden with next time...
I suggest that next time your ds is away that you write yourself a list of things that need doing, or that you'd like to do. Decide which you are going to do (watch that soppy film, or clean out the kitchen cupboards, or go out to a bar or speed dating with a couple of mates maybe). Find a friend you can 'impose' yourself on if you think you'll end up moping. Make sure you have a glass of wine or other treat to look forward too. And try and enjoy a bit of you time.
Hope you feel better soon
Gilly