reverse cell phone directory/private investigator - all roads indicate an affair

Maybe I was blind. He was alway helping others at a local nursing home volunteering his time even when it meant infringing on our only time to be together which was on the weekend when he worked the night shift and could volunteer during the day when I was at work. I was a little suspicious when he went to volunteer on a Sunday at 11:30 am and usualy went till 3:00 but he said that a few of the nurses and a male volunteer were going to go out to dinner for a xmas celebration for a quick bite at a restaurant. It turned out to be a 6 hour dinner and when I asked him who sits in a restaurant for 6 hours and eats (for we never did he said they did and talked!) he came home at 10:30 pm while I was home all day by myself. Anyway I tracked down online our cell phone records and noticed he made excessive calls to one number (a home number). I was able to look it up and it was a lady (10 years younger than me, 15 years younger than him). I then thought to myself could it be a nurse at the nursing home (also he did tell me that a few of the nurses at the nursing home werent happy there and they were thinking of going to another nursing home and I found tucked in one of his books an application to volunteer there!) anyway I looked up nurses on our state licensing site and found her name. I then called the nursing home and she did work there and came to the phone (I hung up). I now want to track down her cellphone number but you have to pay for that online and I wanted to know what a reputabl site would be to get this information. Also did anyone ever hire a private investigator? It might seem like I am obsessed but I really need to know since he firmly denies ever having an affair saying he would never do that to me, trust him! Trust went out when he surprised me with the divorce. Help!