My SO introducing me as his fiancé

Alecia • Living the good life here in wonderful Colorado! Expecting my first! Beyond scared but wonderfully excited! So. Much. Love.
So my SO has been introducing me as his fiancé lately. He has never proposed and has never given me a ring. He was married previously and has a crazy ex fiancé that he did give a ring too. I just feel like its awkward every time he introduces me to people as his fiancé (yet he doesn't do it every time he introduces me, just half the time) I feel like they look at my left ring finger and don't see a ring. And we have never really discussed it so why is he all the sudden doing it now and only half the time? And of we ever do get engaged I would like it to be the proper way. Especially because he did it properly with his last two exes. I guess it just makes me feel like I'm not as special or he doesn't feel that way with me 100%. I mean I am having his child (he has a 5 year old with his ex wife, so not his first) but we also have a lot of things to work on before we ever get married. Maybe I'm just over thinking it?