Please help me find out if my spouse is cheating on me!?

Hi All, I've recently been observing a lot of changes in my spouse behavior. He never lets me access any of his emails, messages on mobiles, whatsapp, etc. Somehow I managed to peek into his mobile and found messages of his ex girlfriend. Is there any app available in the Android market to spy spouse's phone to receive his messages, whatsapp chats, call logs, etc? I've searched a lot on this and have not found anything.