Hello, My Husband Of 31 Years And His Team Got

Hello, my husband of 31 years and his team got laid off from his job and he was able to land a much better paying job. He immediately let a previous female co-worker know about another similar position that was available. He spared no effort to help her land the job and was able to bring this woman on board. I subsequently discovered on his cell phone a series of related text messages and others in which the woman is extremely grateful and uses many terms of endearment as well as expressions of love. I also found numerous phone calls they had made to each other as well as deleted messages. She now works with him and he is more distant and short tempered than ever but denies anything took place. By the way I am 15 years older than my husband and the woman is 10 years younger than him and very attractive .We have a grown son and a 3 year old granddaughter and I am retired. I am hurt and can't trust him. He works overtime and claims he doesn,t get paid for it, I can't believe anything he says. Other than asking him for a divorce, what can I do?