Only it's Jack he wants holding him, not Alma. :'( :'( :'(
After reading all your posts I paid more attention than usual to this scene when I watched BBM yesterday. Not only is he likely thinking of Jack, has anyone else noticed how he really hesitates before leaning back to kiss Alma? He starts to turn to her, stops, seems to have to pull himself together. It's like he's bracing himself to face the reality of who it is behind him there on that bed - not the person he's longing for.
Such play of emotion across Ennis's face ... tormented, resigned. Can't believe I didn't give this moment the weight it deserves before ...
Thanks for sharing!
You know, I've just thought of something here. I think you're absolutely right that he hesitates before turning to kiss her, maybe trying to remove thoughts of Jack from his mind so that Alma won't see something in his eyes....and there's a parallel there with the dozy embrace and how Jack remembers it. He recalls Ennis holding him from behind, not wanting to see that it's Jack he holds....which is almost exactly the same as here where Ennis doesn't want to see that it's Alma he's with.
Now, the dozy embrace obviously took place prior to this scene, so is it the case that Ennis is finally accepting that he's in love with Jack here? He's obviously thinking of him, can't face looking at Alma, can't be "normal" with her - doing everything but shouting out Jack's name.
Or am I just rambling? 
Ramble away, Lindsey, because your rambles make a lot of sense!

I agree with both you and MississaugaRed about this part of the scene - Ennis definitely hesitates before turning to Alma....it's like he has to quickly snap back to the present, after drifting off to the memory of Brokeback and Jack, and force himself to give Alma what she wants. It's all done in a split second, but that moments hesitation, tells us so much.
I'm not sure if it is at this particular moment that Ennis realises he's in love with Jack - for me, that happened when he had to leave Jack and he collapsed in the alleyway. But it is probably a moment when his love for Jack is reaffirmed - and knowing that he is then expected to make love to Alma, the only way he can do that is the way he did it with Jack. :\'(
Has anyone else noticed how, when Ennis and Alma are lying on the bed, Alma says "come here" a couple of times to Ennis? IMHO, I took this to be Alma trying to keep Ennis where he was (facing her), so he wouldn't turn her over. You can see from her face how much she hates it.