Should i tell his wife hes having an affair?

Ok let me start by saying I didn't know he was married untill after I found out I was pregnant I'm now 23 and just had a miscarriage at 3 months. I'm devastated. He was there for me and took me to drs appointments. He even stayed at the hospital when I had to have a d&c 1/20/10. Our 'relationship' started last summer and honestly I ignored him for 2 months before finally giving him my number (he's 39 and I thought he was just too old). I'm not gunna lie I started to fal for him. I've met both his kids. We don't talk as much now but he still calls me. He talks about her so horridly ...calling her names and stuff. (I know people in the neighborhood who know them and say she is a rude negetive person but still he chose to marry her) she has an idea..her best friend saw us at lunch and told her but he ofcourse lied. His sister and best friend know about me. He asked me back in nov if he left his wife would I want to be with him and I said no because I already know he's a lie and a cheat. He didn't take that too well. Anyways...I know where she works but its a huge business. Should I tel her? How should I tell her? I kind of want to do it without revealing myself as I have enough