My boyfriend is texting another girl

Anonymous
I found messages on my boyfriends phone to another girl, I didn't snoop as he often leaves his phone with me asks me to look at things on it for him, I also have his password. I didn't think anything of it as he does have friends who are girls, but something was niggling at me. I then worked out who she is, his cousins best friend who recently broke up with her boyfriend. I then noticed that there were a lot of messages, far more than he sends me. She lives near him and we are in a long distance relationship. I also noticed he likes things she puts on his Facebook, but doesn't for anyone else, she posted on his wall for his birthday and he commented, he didn't even comment on mine. We were going through a rough patch where he had a freak out, and then stopped sending me nice texts and sometimes contacting me at all.

Should I be worried?

I feel really hurt and want to confront him, I feel like I don't trust him anymore and what is a relationship without trust?
My boyfriend is texting another girl
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