Fiancé is obsessed with another guy...

We’re out of state seeing my fiancé’s mom. We have 1 son and I’m pregnant with our daughter. This guy, Tyler, is the light of my fiancé’s life is how it seems to be. He hasn’t stayed with me and our son in two and a half weeks to stay with Tyler. Now that we’re out of state, Tyler is texting nonstop calling nonstop video chatting nonstop. Well this morning he told my fiancé “send a pic of where you are, I’m ready to post”?? What does that even mean? He wants to post where he is on social media? Why? Their “friendship” has destroyed our relationship. Yesterday he told me I’m an “ugly eater” as I ate lunch. We had even discussed (prior) about moving here. But today he told me I’m the reason he doesn’t wanna move here? I think it’s because hesobsessed with Tyler. Has anyone been in a similar situation? I’m lost and done with me and my son being in contest with a wanna be thug “Tyler”