Real talk: you should not be embarrassed about the person you are dating. And I’m not saying that you need to change your embarrassment threshold; I’m saying that maybe he’s not the right person for you if he consistently makes you feel this way.
You may have heard the old adage that it’s impossible to change a man, and I think that’s true (of everyone, not just men!). You can’t make someone change. They might choose to change on their own but you can’t force them or coerce them.
If you really like him – and your message contains no indication that you do – then you can try using positive reinforcement to get him to change his behavior. If he ever wears anything neat and fitted, tell him, “You look so sexy in things that fit you well.” If he cleans something up, tell him, “I love it when you clean up; it makes me feel so taken care of.” You get the picture.
But, seriously… it doesn’t sound like you’re too into this guy. And trust me, there are tons of dudes in the world who are NOT immature, loud, or obnoxious. You can find one if you want to. Don’t settle!!