NEED TO VENT - little long sorry

Ugh I'm so annoyed and upset . I'm 23 my fiancé is 46 . He has kids a few years younger than me. They're all over at our apt and I feel like an extra wheel or something. I feel unwanted here . They don't talk to me at all. His daughter came over and is now making dinner . I feel like I'm being taken over . I went on our bedroom just to chill and he got mad said I was being anti social. I'm sitting on the living room floor because his kids are sprawled out on the couch and chairs . Am I wrong to be a little upset ?