I'm Suspecting My Wife Is Cheating On Me

I know you people are exceptional in giving good advice to people because i have been following this tread for some time. Though i am new. i am suspecting that my lovely wife is cheating on me. The reason is that, each time i want to go through her phone, she picks up a fight. Whenever i want to use it for something else, that would be the time she will want to use it. I feel she is hiding something from me but i really want to get an evidence so that i could confront her. Most of the time when she is chatting with someone on phone, she hides the conversation. i wonder why? Pls great nairalanders, what do i do in this situation? I don't want to confront her yet because i don't hv a proof. Please no insult. Thank you