Is he cheating?

I did a stupid thing last night and I went through my boyfriends phone. Him and I have been together for a year and everything has been ok. I have gotten some weird feelings every now and again but he always talks to me and makes sense of everything. I will look over his shoulder every now and again and not ever really see anything fishy. But the past few days I have had this really weird feeling in my gut that something isn’t right. He doesn’t use his phone around me as much and when he does he makes sure it is at an angle that I couldn’t see even if I looked directly at it. So last night his phone was right by me and he was sleeping and I decided to look. I went through all of his stuff and didn’t find anything. But I went to his snapchat and I saw this girl who he had never mentioned or talked to before that I knew of. I clicked on their messages and I saw some weird stuff. I read everything pretty fast cause my adrenaline was rushing. I got really upset so I walked away and took a breath then came back and reread them. They haven’t talked super often in the past but they have been talking a lot more recently. To the point that now she is like 4th on his best friends list. When him and I first started dating they texted and he brought me up and talked about me. Then a few months passed and then he texted her out of the blue and was like hey I’m sorry we haven’t been talking very much recently I have been super busy but just know I will love you always and never forget that. Then she answered and said the same thing. Then a few weeks go by then she texts him on the day of his graduation. She says omg I can’t believe you graduated I am so so proud of you and I know you will do great things I love you and always will. He responded with thank you it means a lot. It’s nice hearing someone tell me their proud of me , especially when it’s you, I love you always. Keep in mind on the day of his graduation I told him I was proud of him more than anyone. I am constantly telling him how proud I am of everything he has accomplished and all he ever says is thanks. A couple months pass and they end up making lunch plans. Idk if they ever went or not tho. Then the other day he texted her randomly and said hey I’m sorry I haven’t been texting as often my phone has been broken but just know I will always love you and am always here for you. Now all of this seems super sweet right? Well he never says he will always love me. Never. I always say I love you and he will say I love you too and I always say pinky promise and he rolls his eyes. I will say forever and always and he shrugs it off. The only thing is he never really has the time to cheat. He is always at the house with my family, him and my dad are best friends, and then when he’s not at the house he is working. And I know he’s working because he works right by my house and is always driving by. The only time I can think that he would be cheating is during his lunch. He gets a 30 min lunch everyday and never texts me during it. Every now and again him and I will have lunch together but not often. I’m just freaking out because idk if he is cheating on me. Idk if they are just really good friends? But even if that were the case why are they talking like that? They’ve only known each other a little over a year. I have never talked to my friends like that. Especially not if they are men and I am in a relationship. Do y’all think he’s cheating? How should I bring it up to him? I don’t want to tell him I was snooping through his phone but at the same time I don’t want this to go any farther than it already has.