Is he cheating?

Hey girls, so I’ve been dating this guy for almost four months now. I like him a lot but I feel like he might be a cheater. When we first started talking he told me that he had cheated and been cheated on in the past by his ex. That doesn’t mean people can’t change, but I went snooping on his social media recently (I just had a strange feeling) and I found that he’s been liking other girls pictures and flirting. We’re not official yet, but he keeps telling me he want to be in a relationship with me. It’s hard to believe that when there are probably other girls in the picture. Also every weekend he goes “to visit home” and I don’t think that’s all he’s doing. I’ve asked him about it and he claims he’s not doing anything. I think he’s going to see another girl (the one he mainly flirts with on social media). What should I do? I like him but I don’t want to look like an idiot if I am right about this.