Boyfriend trouble😕

I am 2 months pregnant with my first baby and my boyfriend has not been as lovable as I'd like him to be. I dont know if it's just me being paranoid but I feel like he's messing around. I went through his phone and saw a message he sent to some girl on facebook. I don't know what to do. I've talked to him about it but he didn't fess up to cheating on me he said it was "just a friend". I want to do whats best for my baby but I love him so much. HELP😩