He wasn't quite sure how to read the Doctor's movements, but it was appreciated nevertheless. It was nice that he was getting so involved in the kissing, and while Jack certainly wanted to continue, the Doctor's earlier apprehension forced him to put on the brakes. Maybe just this would be okay. Maybe.

With the Doctor's new position, Jack had to adjust himself, wrapping one arm around the Doctor and keeping him near while the other hand braced himself on the mattress so he could grind his hips a little more steady against him.