Boyfriend flirting on facebook?

Ok so my bf keeps leaving his Facebook open, and I am tired of seeing messages that seem flirty. Recent one just random telling a girl that she is gorgeous. Previously there was one where this girl was asking if he was going to keep trying to get in her pants, he said he would if he could, and did she like that, and she said she would tease him, and that he likes being teased, etc. Also one day he poked his best friend, who is a chic, in the in front of me. So all this makes me uncomfortable, but at the same time I feel like I may be overreacting. He spends almost all his free time with me, is super sweet and caring....but these messages just make me think he is fishing around, and what happens when someone bites? Should I end this now before I get hurt? I really don't think he would cheat, because of some small reasons.....ahem......but who knows. Maybe he is more confident than I think he should be. Thoughts?