Is it ok for my husband to secretly text other women?

I was getting suspicious and checked our cell bill (which I never do) and found out that my husband has been secretly texting two other women. He says one of them is an old friend. Her name is Nancy and in his cell phone book, he put her name as Sgt. Nan (he is in the Army). That was to hide the name obviously. He has NEVER mentioned this woman's name to me in the 5 years we have been together. The other one is his ex-wife, whom he has always said he despises. There are hundreds of texts in the past month to both of them (more than to me), but none before Dec 11. Some of these texts are forwards about , and other stuff that he would get from his male friends. I know this because he forwards the same crap to me and the times coincide with each other. When I have looked at his phone, the text history is cleared, so I started to get suspicious a couple weeks ago and finally checked the bill today.