Please stoppppp!

How can I stop creating false thoughts? I’m newly 24 and I have a new job (RN), which is already stressful enough. I keep thinking of things that I THINK people are thinking about me (confusing, right? It’s frustrating dealing with this.) It’s completely assumption after assumption. It doesn’t help that the people that I work with gossip like no other so sometimes I think they talk about me when I’m not around. It further drives my assumptions. My brain is a scattered mess. I really want to stop these false thoughts. Please help.....