This happened to me except my bf did sleep with the girl. Then he had to go on working with her and I hated it, but he could hardly sack her (imagine the implications). I do think if he had carried on seeing her in a social context I would've been really unhappy with it. I had a go at him about stuff like why did he still have her no in his fone, and he said he had to have it for work, which was plausible. When she left the company I watched him delete it! GillR, I would tell him exactly how you feel. It is a tough situation but if your bf is doing something that makes you feel let down and sick on a regular basis, you're just never gonna be happy and secure. He needs to assess his priorities.