Would a girl lie about an std?

I been talking to this guy from work for a while now. So yesterday this girl from an unknown number called me saying " Kim. I know you don't know me but I found your number in toms phone and I seen the text messages and I want you to get yourself tested" my heart drops because how did she get my number and how does she know my name. I'm freaking out then I tell her I didn't even know he was talking to other girls. She says " I know me and him just got into a big fight and he wants to talk to all theses girls and be single but I think I should let you know he gave me herpes and you should get tested" I ask tom about it(I still have not told him that I found out he has herpes I don't really know how to tell someone that) and he denied everything saying its people from work playing a joke on me and that the Girls are just jealous. I don't believe him nor do I trust him. He knows calls himself my boyfriend and wants to be with me but I like someone else plus tom has to much drama.