I am going to go over this exactly as I read it, Em.
Sounds good to me. But...
'I'll lock you up in my love'
Not sure when I read this line. Genuine loving sentiment or more the stalking insinuation of The Police's 'Everywhere you go'? I did, however, enjoy the subtle alliteration here between 'lock' and 'love'.
'then throw away the key'
Oh dear. 'I'll be watching you' is beginning to play loud and clear in my head here with that chilling bass line... Still, it could yet be positive!
'as I want this intimacy'
At least we know you want to be intimate with this person and not torture them to death slowly, But still, when passion reaches such extents it can sometimes become sinister, so I am still not sure what is meant by this poem quite yet.
'between you and me'
an extension of the last line, in terms of how I interpret the poem, anyway.
'to last for all eternity'
Okay, you are clearly very much in love with this person and have no immediate intentions on their life, but whether you intended it or not, I do enjoy the rather dark ambiguity of this poem. Innocent or worrying?
By the way, I do appreciate the same end rhyme in lines 2-5 - not easy to do always.