AITA/ broke up with boyfriend

I (F,21) have been dating (M,21) for 3 years, we have been going through a rough patch, hardly seeing each other due to work and a lacking of effort on both parts and a lot of arguing. I had a gut feeling he may of been cheating. I asked to check his phone and he said no. he works at a shop so I went in to get some wrapping paper for his birthday and saw him. he had a gold star sticker stuck to him. I went over to ask him and jokingly bought it up and saw him panic. right then a girl he works with walks past and stares at him, I ask whose that and watch him panic. I leave the shop upset and message him “come and see me after work so we can talk.” he comes round and I say “I think your cheating can I check your phone please“ he says “no” I say i want to check your phone to prove your not cheating or we break up because I’ll assume your hiding something“ he says “your not checking my phone I’m not and you have to trust me“ we broke up

am I the asshole?