Making me suspicious

We’ve been together 4 years now and have 2 kids together, but I’m starting to think your cheating. I occasionally go threw your phone (you know that) to find any pictures of our kids that I like to print out. But recently I’ve noticed your more protective of your phone! Your in the basement more, your staying up later. I’ve also noticed you’ve been texting some girl name Chelsea (I’ve got good eyes when your sitting next to me in the car) I asked who you were texting and you say James but James never texts you he always uses fb messenger. I went into your messages while I was looking threw pictures but I noticed you deleted your conversation. I don’t know what to do or where to begin but if your cheating on me I wanna know now so I can leave 😔