I'm a chef and I've been living a lie about being pregnant.

I'm an actual chef. I work in a high end restaurant with a great reputation and the owner is amazing. He and I became friends over the past year and he even introduced me to his son and daughter who are in their early twenties. He asked me out to lunch the other day and explained he wanted to talk to me about something and that he needed to trust me with a secret. I agreed to keep whatever he told me confidential. He told me that he had a sexual encounter with me when I was working as a line cook at a different restaurant and that he was afraid my new boyfriend (who works as a personal chef at a different high end restaurant) might find out and get upset. He also told me he had a sexual encounter with my boyfriend when he was working as a line cook. I'm livid that he told me because I don't think what he did is that big of a deal. I'm just mad that he told me and also that he's cheating on his wife. I'm trying to decide if I should tell my boyfriend but I don't know if it would make any difference.