Should I be concerned?

So my boyfriend and I have been together for a few months now. Relationship is good, sex is great, we have been going strong so far. But there is one little thing that bothers me.

He likes to kinda make fun of Plus size girls. Now he never gone as far as to call them ugly or say horrible things to their faces. But he'll make small side comments like "here come a biggie" or "She gets on this bus it wont be able to move".

Now what confuses me is that I weigh 310 lbs. Im tall so i dont look my weight but im still a typical size 22 jeans, 24G bra, kind of big girl. (Its all butt and boobs for me lol) And these girls who he makes these comments on are usually smaller than me.

Oddly its making me feel self-conscious of how i look. Did he once call me a "biggie"? If hes attracted to me then why does he make fun of these girls who are all very beautiful?

I tell him to stop playfully but honestly should i have a sitdown talk about this?