j,

Perhaps something happened recently that either scared him about your safety or himself, or worried him about his losing control? Perhaps he is trying a mindfuck but it is not coming out quite right? (or perhaps it is, and you are getting totally pwned.)

It sounds like either:
A) Something happened that worried him/freaked him out and he is now nervous
B) He is taking the BDSM relationship for granted and is not realizing that there is as much give as take in the D position

or

C) He is getting wwaaaaayyy inside your head and twisting little knobs in a very clever way

Sounds like you are doing most everything right, and if the answer is C it sounds like you're in for a whole lot of begging, pleading, and showing him how important his domination is to you before you get your spoils.

If it's A or B, then it will require some honest, open discussions with him to figure out what's going on, and how the two of you can work through everything together and keep moving forward. It sounds like you have a long, successful relationship with him, so I feel confident that you will find a way to communicate and work things out.

In the meantime you have my sympathies and best wishes