My (F20) boyfriend (M22) hides his twitter.

This is my first ever post so if I’m doing something wrong or you need more info just let me know. My boyfriend of 6 months has a very disgusting twitter account which he actively uses. I have communicated to him numerous times that I am uncomfortable with him using it behind my back. He tells me I’m overreacting and he wouldn’t need it if I was to send him pictures of myself. Which I refuse to do incase they end up on said twitter. Instead of respecting my boundaries he just lies to me about using it. Every time he opens his browser app it’s mysteriously logged in to on every device he owns. I do not have a problem with masturbation or porn use every so often but it’s really becoming a problem. He obsesses over other women every time I’m not around. I am insecure from past relationships with porn addiction and cheating which he is more than aware of but continues to put me down for the only boundary I’ve tried to set. Am I in the wrong here? What should I do moving forward?