hi molly
i over think as well, sometimes i can hear my manager and the team leader whispering and i would think they were talking about me and work myself into a frenzy, after awhile i realized it wasnt about me....now i either put on my headphones or i just tune them out and focus on my work.

you are there to work, so do your best and try to block others out, i know easier said than done...so perhaps like the other's mentioned seeing a therapist would help.

good luck !!