So my dad is having another affair...?

Ok so here is my situation. My dad several years back had an affair with a co-worker, and now i have a little sister because of that. But my parents stayed together. Anyway he has moved to another store/another company. He is always talking to this new current co-worker. 19 hours last month on phone. The thing is she was moved to another store, dont know why. I feel like it could be that there was stipulation that the two were having extramarital affairs. But last Thursday my mom got a weird feeling that he was not at work like he said he was, well she called the store and they said he wasnt. She then called the other store to see if the woman was there, she wasnt. She later checked the phone records and it showed he was in a town way far from his work and close to hers. My mom asked him where he went and he said nowhere he stayed at work. When me and my brother confront him he still DENIES DENIES DENIES, saying we are delusional and mislead. Im 18 and really dont now what to do at this point, my mom told him she wants a divorce. I feel like he is just scared to admit because he knows he will lose me and my brother and a house that all of us had built together. Its just weird he is always talking to this woman, he doesn't really hide it except he goes to a private place to talk to her, and also he says they are just friends, which the must at least be cause he spends hours a month talking to her, but they arent even friends on facebook; he is friends with other co-workers What do you think?