I think the key is finding things that you can do in your day to remind yourself that you are a sub. Ask him to set you some little tasks, that won't give you away. For example, I have to pinch my nipples for 50 seconds each time I go to the bathroom. So even when I am at work, I am reminded I am his sub in this way.

The idea of regular contact is good, but not always possible I know. Maybe instead have a regular time where you email or text him.

As has been said above, I feel the key is to have a bit of a routine to your day, so that even on those days when you are not able to talk to him or see him, you can still feel his presence. Not perfect I know, but hey, it is better than nothing.

I also would not get too worried about him being freaked out over what you like to do, after all, it seems he likes the same things! I can understand how strange it is to tell others this big secret so many of us work so hard to keep secret. I think you are very lucky to have found someone who you can both enjoy being with and who shares your kinky desires. Just have fun with it, even with the frustrations of the moment.

Good luck honey.