Boy, do I know what you are going through. We have 3 that went off to college. My boys are 18 months apart/2 years in grade. It was soooo very hard when our oldest son went off to college (8 hrs away) but at least we had the other two.
When our second one went off....it was very strange, with only our youngest (and only daughter) at home with us .
When she went off to college (which was the same one as our 2nd child and 11 hrs away.) it was devesting......for me!

Her and I were very close and still are very close to this day, talking almost everyday. The only comfort I had with her at college was her big brother was at the same college and just a few blocks away from her.
I cried every time when it was time for ALL three of them to go back to college after being home for a break. I would walk past their rooms and cry, I would smell things that would remind them of me (fabric softener

) and cry.
All three have since graduated from college and are living away from our hometown. They all say they would love to move back home someday, but right now jobs are keeping them where they are. To this day I still cry when they leave after being here for a visit.
My husband and I have filled the void with being with just us two again and of course with Moose. My husband says I am more neurotic over Moose than I was with the kids
But hang it there.........it does get easier, especially knowing they are healthily, happy and successful in their lives. And by the way....It does it fun again: doing what you want, when you, where you want

not worrying about the kids being home.
Hugs to you!