"I love your bum!" "I am not FAT!"

The title line refers to an incidence that happened a while ago, it went like this:
Early morning, I was already up and had just returned from taking a shower and doing my morning self-inspection, to see whether I had gained weight somewhere.You probably know the routine, if you have a large mirror in front of you, you look at yourself and sometimes rate yourself, legs nice, breasts ok, bum, ... .
Back in the bedroom I found Master watching me, while I started dressing and he said something that I knew was meant nicely, because he had his positive and admiring looks, which is a real contrast to the strict and 'I am all in control' looks he can do: "I love your body, you have lovely legs, lovely tits and I love your bum" Oh what a killer in that moment. I was still dealing with whether my bum had become huge or only large when I had returned from the shower and then he started so nicely and ruined it by mentioning my bum.
My excuse now: I was not rational in that moment. My facial expression then: How could you say something so nasty to me. My answer: "Do you think I have a huge bum?" He was still at ease then, but I was immediately agitated. He was still playing along, I think up to that moment Master still thought it was a relaxing moment "all fine, you are just right the way you are." He said a bit more, some of which I really loved to hear, like I am beautiful, I think that is lovely to say, but since he did not really answer and I was  out for only one piece of information at that moment I asked again, which was already daring from my side, because if he did not stop me in time, I might just end up in trouble, with a red bum. Sometimes I can't stop myself and that's another reason why I am on the receiving end.
Master obviously wanted to be nice but then he mentioned something like I am not too skinny and not too curvy either, just right. What a feast, if you want to pick on someone. I swear that I did not want to raise a quarrel, but I heard the wrong words in the wrong moment and did not listen to the real meaning behind them and was still with the 'not too skinny' part. "So you do think I am fat?" He saw that I had a real issue at that moment and was not reasonable at all. He came up and hugged me and told me to stop being self-destructive, assertively, but not as if he intended to punish me, he comforted me a lot instead, just that, and I got a lot more lovely things to hear from him, but not another word about my butt. At that time I could listen to what he said again and the whole episode was over right then. We talked about that later and although I have become better with the bum-problem all in all, I have to admit that the self-esteem issue concerning my looks is still not solved completely.

This is something I really feel self-conscious about. If Master says something like 'I love your bum', chances are high that I start wondering if there was an underlying message for me, like, my bum is too big, I should go on a diet, I should do more physical exercise or similar things. Sure, whether I have doubts about my appearance or not depends on how well I feel emotionally, but most of the time I don't feel emotionally challenged at all, feel well, unless my close friend PMS has arrived again. I am grateful that Master knows how to deal with me in such situations, and I know that the problem I have here is connected to self-esteem. We are working on that together, and from Master's side I get all the support I could ever wish for. He wouldn't want to change anything about my body and always gives me the feeling that he loves me, body included, and I am all happy about that.
But nevertheless, if statements about my looks come in the wrong moment, they leave me with some lurking doubts and I need time to get rid of these again. At other times, I might not care at all about a statement which would have left me in doubts in another moment, still I have these fits and hate them, because I have learned that it is silly, but on a deeper level, it has not sunk in completely yet. But it has reached a deeper level than last year, because I can laugh about it, and Master can even tease me a little bit with that sometimes, but only about once a year.