Im sorry we cant act as a therapist with you, talking you down from your anxiety. what we can do is tell you what has helped ourselves..

the first thing I do when my wife has plans to go out of town is I contact my treatment providers (medical doctors, therapists, psychiatrists...) and together we all develop a plan of how to take care of myself and my anxiety.

then i just follow my treatment plans. example....

my treatment providers and I exchange contact information, i keep mine on both my house phone and my cell phones, that way regardless of where I am and whats going on I can contact my treatment providers.

my treatment providers do medication adjustments so that my meds can handle the added anxiety levels I am in when my wife has to be out of town.

I also plan activities like visiting friends and family, outings with my children, take in a movie or show, take myself out to dinner....

at home I plan what tv shows I want to catch on tv and internet services.

journal and other lower my stress level activities that I normally do...

my suggestion is since each person has their own things that work to lower their stress and anxiety the best move for you is to contact your or a mental health treatment provider and your physician, they can help you to develop an emergency plan on how you can handle your anxiety while your boyfriend is out of town.