In a relationship without being asked...

Idk if this only happens to me but I'm literally in three "relationships" with 3 different guys because they just decided I'm their girlfriend. We've never had a conversation about it they just start referring to me as their gf/them as my bf to other people and myself. If you ask me I'm single. Idk how to break that to them though. And is it weird that this happens to me all the time? Am I sending off some weird vibe that asking me if I want to be official isn't necessary?