He feels that the exact moment of her embracing is priceless. He takes her as his only possession. Despite his elaborate justifications for his act, he has, in fact, committed murder, and he expects God to punish him or, at least, to take notice.
The "Porphyria" persona's romantic egotism leads him into all manner of monstrously selfish assumptions compatible with his own longings.
He looks up into her face and realizes that she "worshipp'd" him in this moment, but that she would ultimately return to the embrace of social expectation. What is the relationship between the two?
Entire Victorian culture was based on the male perspective. Porphyria is a mystery. When no voice replied, She put my arm about her waist, And made her smooth white shoulder bare, And all her yellow hair displaced, And, stooping, made my cheek lie there, And spread, o'er all, her yellow hair, Murmuring how she loved me — she Too weak, for all her heart's endeavour, To set its struggling passion free From pride, and vainer ties dissever, And give herself to me for ever.