Please advice.. Wife cheating

I'm from India. Arranged marriage. My wife always has short temper hence my married life isn't very happy. Also, she's been always engaging texting & calls with my cousin. She hides her phone. I can't touch her phone without her permission. I accidentally found a message on her phone from my cousin saying how much he enjoyed neck kisses, and wishes it was lips kisses. Our marriage is 8 yrs, have beautiful daughter and son. In India things are different, I just can't divorce her, I'm more worried about my kids growing up without both parents together, on other hand it's killing me knowing my wife is a cheater I'm lost, I haven't asked her about the text message. I'm quite weak person, not leader, I'm coward for fight or arguments. I'm kind lost, which way to process and move forward. Any advice if anyone knows about Indian marriages and social pressure of staying together?