Bf doesn't want to go public

My bf and I have been togethor for 1.5 yrs and he never wants to post any photos of us on any social media. He's the type of guys who post everything they do on social media so privacy doesn't seem to be an issue to him. Deep down I think it's because he doesn't want his babymomma to find through their mutual friends. Somehow he always has an excuse of why he can't. It seems shady to me. He's hiding something and I know it. Once he told me if I post with him to not tag him. I said are you fucking serious? He said he was just joking but I don't feel it was a joke....

Any thoughts?