Foreign Soul, I assume he is talking to other people and being his normal self around them. Is that correct?

Has he ever acted in a passive-aggressive way before? Ever given you the silent treatment when he gets upset with you?

Maybe you should consider confronting him, asking him what's wrong, is he upset with you? It actually could be he is getting cold feet about the wedding. After all, you two were together all those years without being married....And maybe he is seeing that's the way he would prefer.

Of course, I don't know for sure.