Boyfriend has a girls number saved under a guys name

Me and boyfriend have been working a lot. We don’t have much time together besides maybe 30 minutes of tv time before we have to go to sleep. Today was the first time in weeks we finally had sex after I put our child to sleep. Lately we’ve been arguing a lot because he’s changed. He’s become less patient, less loving, and even though he’s physically with me he’s not really there. It’s like he’s always in a bad mood when we do things as a family. It doesn’t matter whether we’re going grocery shopping, on a quick target run, or even to the corner store. I’ll say something and suddenly it’s like I’m annoying him and he’ll demand we go back home. And when we’re home, he’s either playing video games or has his eyes glued to his phone. He’s never denied me looking at his phone. I’ll ask and check who it is he’s chatting with and it’s always his friends. We’re still young he’s 27 and I’m 23 so I get him wanting to relax and spend time with friends but I’m ready to settle, give our kid a successful and healthy life , & spend quality time with her. Make memories as a family shell always look back on and remember while he literally just wants to be stuck behind a monitor playing video games. Anyway he fell asleep and I couldn’t help my urge to go through his phone. Everything was clean so my last stop was his contacts and I came across this contact name. I thought it was weird.

I don’t know anyone by that name and I know all his coworkers and friends so I decided to reverse look up the phone number and turns out, it’s a girls number. I use his phone all the time vice versa and I’ve never seen this contact pop up. Idk if he just didn’t want to put her actual name because he didn’t want me to wonder why he had a girls number. I’ve been with a serial cheater before and he knows I don’t take lies and secrets lightly. It’s 2 in the morning and I can’t rest. I have to wake up in 2 hours to get ready for work. I probably won’t even see him till 6pm today. I don’t want to accuse him of cheating but this is so suspicious and my stomach is twisting up.