Oh Frankly, do I know those feelings.
One of my biggest challenges was to figure out the difference between "normal" empty nesting feelings... and the weird crap brought on by addiction, because for my kids everything hit at the same time.
Today, I know that some of the big stuff I was dealing with WAS the letting go of my kids and allowing them to walk whatever path is before them. Allowing MY dreams and hopes for their future to die... after nuturing those dreams for over 20 years.
My youngest has been out for 3 years, now. It has gotten better. But I did sleep with the phone off the hook for a long time in order to get a good night's sleep.
(((Hugs)))