Hi Jennifer
Aren't those "what if's" the worse? You are not alone and reaching out to us here is a great way to help.
An idea I have is to sit down and explain to your hubby how worried you get when he isn't home....especially overnight. Ask him if he could give you a quick phone call (quietly so his buddies won't tease him about it

) and just to let you know that he is there...having fun etc.
What you then need to do is stay busy that night. Do you have any close friends that could come over and spend the evening with you? Watching movies....playing a board game, etc? I know it is easier said than done but try it.
Before you know it he will be home

. I think explaining how you feel to him (be sure to say "I" feel panicky when I am alone, etc). It will help both of you.
Good luck and you can always come online here too.....there is usually someone in chat that you could talk to then as well.

Heather