Hi sd167,
It's common for them to distance themselves from people - especially the ones who are closest to them. My boyfriend and I have been together for three years, and he still has his episodes of retreat.
Yes, in my experience it's best to give them time and space. And unfortunately, time is a totally different concept for men than it is for women! It's different for each couple, but in my experience I give about a week, then I send a very short "Hi, hope you're doing well." I don't ask questions, just a quick text or email to let him know that I'm there if he needs me. If there's no response, give him more time and space.
I know what you're going through, and it can be very frustrating and really spike our anxiety level - You're left n limbo. But please remind yourself that it has nothing to do with you, and if you need to hear it, you can always find me here=)
~Spring