maybe an off topic but a always want to know was Jack hurt on the fisrt sex? seems so quick with no prep...
In real life, I don't see how someone in Jack's position could not be hurt by the rough tryst we see in that scene--not to be vulgar, but saliva does not good lubrication make. For the story and film's purposes, perhaps we are being implicitly asked to suspend belief a little bit at this moment.
On the other hand, maybe we are meant to infer that Jack did hurt, yet nonetheless submitted to the experience (which he, after all, initiated). He was so attracted to Ennis, and possibly even already in love with him, that even this rough intimacy might have been more than welcome to his mind.