Quick relationship question

My bf of 3 weeks left his phone in my car at lunch. In that situation I had to unlock his phone. I already knew his passcode and he knew mine but we’d forget. Moving on though sorry if it’s a bit scattered but I had to use his text messages because the number he called his phone from was not answering I called 3 times within 5 minutes and I texted 3 times. As I went to text messages I saw his exs name I just closed his phone back up and freaked out the whole day I’ve been an anxiety mess, felt so much physical pain for it I had to leave work early and he’s been asking why but I couldn’t say why I felt so bad for even going on his phone I apologized but also he told me he blocked his ex from everything and doesn’t talk to her but he obviously lied. I asked him do you feel bad or remorse he said no. He did say sorry though. He got all quite and said I gave him anxiety I apologized profusely for that and as well as me reading his exs name. I didn’t go through the messages because I’d feel awful after but I don’t know how to feel. He lied about not talking to his ex. He said he was just worried about her in the messages. I said ok I just wanna know why you lied. I asked him to promise that he’d never lie to me again but damn he misused my trust already. He fell asleep rn and I’m just at his house supposed to sleep over but I don’t know what to do. He was supposed to be the one… smh I am kinda hurt that he lied. We’re both 25. Thanks sorry for bothering y’all

Merry Christmas :)