I agree, see a lawyer--no obligation and it can help a whole lot to know what your rights and obligations would be if you divorce.
Second, contact your local women's shelter or the National DV Hotline and talk to an advocate. It sounds to me as if his behavior puts you in fear (beyond just the fear of emotional upset from having to watch drunken behavior)--you might qualify for a protective order that would require him to leave. You are pregnant, you don't need the stress. You also have your young child to think about. This is terribly confusing and scary for a child, to live with this kind of behavior.
Hugs,