For me,definitively this "I´m not you,Ennis" includes a whole lot of circumstances,feelings,needs and longings that are seen in different way for both of them,or at least,it seems not to have the same level in each one of them.From,obviously,"My libido is not so in control as yours,so I can´t make it with a couple of ...",to "Nor I have all my life´s aspects so in control as you seem to have yours"; passing by "I just can´t have enough with seeing you a few times a year,I need your presence more often", or by "I need really living with you and I´m willing to let everything behind to get it, and you seem to need only what we get during all these years".
Not,really,Jack was not Ennis;he was fighting all his short life to get his dreams, while Ennis was suffering a lot-maybe more than Jack-because he must hide his deepest and most loving feelings and longings to build a strong man´s shield-before everybody,society,Jack and also himself-.Perhaps he needed and whished all this the same or even more than his lover,but he needed also,he MUST, not to show it.Such a pity. :\'(