caught my boyfriend

so my boyfriend and I have been together for 4 years and this past year we got a dog and just recently bought a house together. he has been acting weird towards me for a few weeks, and i ended up having a got feeling that he was being like that because of another girl. i looked at his phone (which i shouldn’t have and i know that is wrong) and i found 3 different things that all raise red flags for me. he just got a new job but i found messages from a girl at his old job. in these messages, she acknowledges he has a girlfriend to which he says nothing and continues to press her. secondly i found pictures of a girls ass, which he told me he saved from the internet. and lastly, tik toks showing off various girls’ bodies as a trend. im so hurt and feel such a pit in my stomach bc i feel like I’m nothing to him. i feel like this because he was looking at other girls and messaging one while we are together, so what good am I to him? I’m sad and hurt and now i feel stuck having just got the house. we lived in an apartment for a year before we got our house and our relationship has always been serious. i can’t help but blame myself that i must be doing something wrong.