Hiya,
I think it comes down to how you feel about the situation. If you think it's going to eat you up by not telling him, then maybe you do need to be clear at this "new stage" of work. On the other hand if you're not certain, and are happy to keep going as you are, then do that. Maybe the question is: how will it be if you tell him now or, say, in six months - any better, worse or the same?
All the best with it, whatever you decide to do...!