What do I do

So. His entire attitude is NOT healthy and he seems to be super childish. ALSO people who accuse their partner of cheating are usually actually cheating themselves. So be on the lookout for that. Go get tested for STIs right away because if he's cheating on you he is likely exposing you to a lot of risk for potential disease/infection. You should either leave him or think really hard about leaving him. Also you should kill him in the head with a large rock or small boulder.

EDIT also here's a link to a free PDF of a book you (and every other woman on earth) should read through. Extremely eye opening stuff. It is called Why Does He Do That and it is by a man named Lundy Bancroft who worked to rehabilitate abusive and manipulative men. It is very straightforward and will be very useful to you when dealing with men all through your life.
https://freebooksmania.com/2021/01/why-does-he-do-that-pdf-free-download-by-lundy-bancroft.html