But it’s hard for me to decline because having sex seems (artificially I know) like a temporary return to normalcy in our M. If I start refusing him altogether, it’s one less thing tying us together. I don’t even know how to broach the subject of feeling used in sex. Stop him when he’s making an advance? Initiate a conversation about it?
First and foremost you have to decide if you want to have sex even knowing that it doesn't mean much with respect to reconciliation. If yes, there's not much to talk about. If no, then yes when he makes an advance is probably the time to tell him you're really turned on but only will if----xxxx----whatever your terms are. Maybe also consider what your terms were the first time you two were intimate.
