My boyfriend [26M] keeps making me [20F] feel insecure but I feel like it’s my fault

Me [20F] and my boyfriend [26M] have been together for 4 months and it's been great for the most part. This was my first serious relationship in my life and his first relationship after three years of celibacy. I never considered myself to be some sort of stunning beauty but I do love the way I look for the most part. I really value the time I take to make sure my skin care and makeup routines are perfect and spend hours curating the most flattering outfit for my body type. The amount of men who have approached me also somewhat confirmed to me that I was at least a bit pretty.

That being said one of the most common comments people make on my appearance is that I'm too skinny. I had dealt with an eating disorder my entire life and only went into recovery a two years ago. I'm actually really proud of how far I've came however I'm still underweight and look the part. I have no figure and am as flat as a door. Because of that I constantly having people telling me to gain weight and workout so I can fill my figure. However I don't put any weight behind their words cause I'm just proud of how far I've come.

My partner has never judged me for being skinny. He once made a comment about how I was even skinnier than his best friend which he didn't think was possible. I chuckled and moved on. However he will constantly make comments about how much he loves big boobs and butts and I have neither. We were once talking about our sexual preferences and he talked about how he likes having something to grab onto which I don't think he meant it as a jab to me but it did bother me a bit. Then there are times when he'll show me a video that pops on his feed of a curvy women and he'll comment how she has a nice ass. He says it jokingly and always makes sure to follow up by saying he only has eyes for me and while the teasing doesn't bother me it's the fact he's attracted to something I don't have that makes me paranoid. The other day I was looking at gym clothes and was talking about how I can't tell if the shorts look nice or it's just the models body and he just commented that everything looks good when a girl has a nice butt. Again I don't think there's any ill intention behind his words and I honestly had the same thought but just hearing it come out from him makes me insecure.

I understand my bf is not responsible for my insecurities especially since he doesn't know my history with ED and he's never actually told me to change. I know he loves me and he constantly tells me how stunning I am and how he loves having a pretty gf but I can't help but think if I'm just pretty and not hot. It's even gotten to the point that I'm considering working out to try and build a bigger butt. And while there's nothing wrong with working out I think the fact that I know that I'm subconsciously doing this for someone else will cause me to relapse and start becoming obsessive over my figure and weight again. Even worse I'm afraid that if I do grow my butt that he will find me more attractive and I don't think that would make me happy cause the only thing that would cross my mind is that he was settling.

I'm self admittedly pretty conceited as it is and have never done anything for the approval of others. Even when I was in active ED I did everything because I wanted to look a certain way even though majority of those around me didn't find it attractive. But now all of sudden I want to change so my bf can like me. It makes me wonder why he even chose me if I don't have the body type he likes. What can I say to make him stop making these jokes. I feel like telling him "hey I don't like when you tell me you like big butts when I don't have one" sounds silly. Not to mention even if he were to never mention it again the damage has already been done. I know he finds a different body type attractive. And while I know that align with his type aesthetically speaking the fact that my body type is different bothers me soo much. Do these feeling ever go away.

TL;DR My bf makes passing comments about how he thinks women with large butts and boobs are attractive. However I am very skinny and have no curves. This makes me feel insecure and I don't know what to do.