my boyfriend flirting with other women on social media?

[Ashlyn]

My so called bf of two years have been flirting with other women on sites like fb, twitter...ect. My main issue is his fb I am not a friend of his but through happenstance and some fb stalking I saw questionable post. He doesn't want me on his fb cause he claims I get angry over dumb things (I know lame excuse). Anyway recently I saw him write a post to another women and in it he wrote kisses to her. Also recently he was commenting on a muteral friends post-the original post was about sex and in the comment section another women named jessica was posting, he wrote jessica can join me. I find this very disrespectful and considering ending a 2year relationship. He says I'm being ridiculose and jealous, n none of it means anything. Wondering what others think. Fyi he's proven himself in the past to be untrustworthy.