hi. I'm a crazy person too.
I don't have any issues with being home alone but I have HUGE issues with constant worry about something terrible happening to my loved ones. I also have a way too overactive imagination and can work myself up in 5 seconds flat if I allow it. Distractions help a lot. and exhausting myself physically helps a lot. Writing down exactly what I'm worrying about help too. For some reason seeing it in black and white helps me see how silly some of my worries actually are.

Would planning a special 'you-time' night while your fiance is gone maybe help with the anxiety? a spa night? or an eat ice cream straight out of the carton night? or any whatever-your-favorite-hobby is night?