How can I catch my husband if he is cheating on me?

After 12 years of marriage, my husband has been acting secretive, staying out late, and is very protective of his phone. I’m almost certain he is cheating, but I need proof. How can I find out the truth without him knowing? This is causing me a lot of stress, and I just want answers.

Gather evidence discreetly, like checking his phone or messages if you have access. Be aware that spying can backfire and cause trust issues.