Boyfriend talks about me with other people?

So we've been dating for a little over a year and a half and I'm a proudly independent girl. With that being said, I do a lot of my errands on my own like shopping, getting groceries, post office, walk my dog alone, you name it. But I HATE that my boyfriend says things like "I hope you don't find a new side piece", "we all know your neighbor is your new side piece" (never spoken to my neighbor), "I hope you don't find a cute boy and replace me" and it just ERKS me when he says those things. It's fucking annoying! So I say please stop saying those things they make me upset blah blah blah and he says "Baby you know I'm just kidding! You shouldn't be upset if it's not true. You should just tell me no I love you blah blah and laugh it off". So he makes me feel guilty for getting mad at his constant "jokes".

The dude is 21, I'm his first real love and he says he has plans to marry me later in life etc. I know this is just his insecurities coming out but god damn it's annoying! The problem is that everything other than that is so good and perfect! It's just this one long "joke"..

How do I get through to him without blowing a fit? Anyone else have/had this happen to? Anything else your SO did or say? Anything helps!

P.S I've never cheated, never lead guy friendships get in our way, never on social media, don't dress to impress, don't make a a lot of eye contact with guys my age etc! I make it known I'm not looking for a guy as much as I can 🙄