The best answer is just to hang in there, because it will change. :) But sometimes I find it helps if you stop looking for "signals" and instead just start concentrating on what his body must feel like to him. If you are picking up on him being uncomfortable, and you don't know why, you should potty him. With Mo, I'm finding that there is no one sign or signal that I pick up on in him-- instead, it is a feeling in me. I become aware of being mildly anxious that he is fidgetty and I don't know what the matter is and no position I put him in seems to put him at ease. That's when I know to potty him.
But seriously- if he is working on something developmentally, you might not get any signal at all! Doesn't mean you are doing it "wrong" at all, either. Just hang in there. EC is a long term relationship. :)