did you cheat on her or flirt with someone and she found out, or said anything through texts she might have read on your phone, she doesn't seem to be into sex with you now and there has to be a good reason. the " won't let me see her body " is strange, you are engaged and obviously she let you see her before, could she have been sexually assaulted and didn't tell you?
why can't you straight out ask her wtf is going on with you?
When I tell the truth, it is not for the sake of convincing those who do not know it, but for the sake of defending those that do.
William Blake