My DH is also away at the moment, so I am very aware of your anxieties.
The time leading up to deployment is always much worse and you'll hopefully find that once your DH has left, that after the initial few days your adrenalin and coping mechanisms will kick in and you'll just get on with it.
Things should probably change for the better when your DC starts school. That will open up new opportunities to meet people and you'll embark on the whole play date thing, which may well introduce you to new friends & adult company, which is a godsend when your DH is away.
Has your DH gone on his own, or with a unit? Are you in Germany? I so, where? We spent 6 years in Germany, in various locations, and some are definitely better than others.
You should definitely take advantage of your (2?) paid trips back home & would any family be able to come out, even for a weekend, to give you a break and a couple of lie-ins?
Your 5 month old will settle down with sleeping at some point, hopefully sooner rather than later. At least if DH is away, you can head to bed when you're tired and not feel as though you have to stay up.
Is there a nursery or childminder that your little one can go to, even for one morning just to give you a break?
The things that helped me were allowing myself a babysitter at least once a month (and your social life will get better with school & as you get to know more people) and also exercising - whether in your sitting room or a run, if a friend could mind the little one for 30 minutes. Could you start a book club if there isn't one already?
Just shout if you have any other questions!
Good luck - remember: the lead up is always much much worse xx