I'm not sure what you are asking in this post as I'm not sure what your T is expecting by having you "pay attention to the messages of my mother". Like others have posted, the messages I identified were not spoken ones but more narratives that were created through many different "minor" comments and actions that occurred over my childhood that I combined to form an understanding/narrative of myself.

One narrative was that I was always fat. I don't know when this narrative became my narrative, I remember being in high school/college with it. I took out my baby book that had my weight/height recorded at different ages until I was 15, my memory of different things that gave me some perspective of potential weight at ages up to 20... and then my school pictures throughout my entire childhood to figure out a BMI at different points in my childhood only to come to find that it wasn't until I was 14 that I technically reached overweight per BMI charts and in 5th grade when I was put on my first diet, I was technically on the lower line of the BMI chart, headed towards underweight.

So where did this narrative come from and who's was it? Going into therapy, I had known that my mother considered herself fat as a child until middle school. Through discussions with my mother as I processed elements of my childhood in therapy, I found out that she'd restricted my eating from early childhood on for fears of me becoming fat.

My mother never told me I was fat... directly. More the usual comments of how I'd look cute if only I lost... or that doesn't look good on you at this weight. The bottom line is - this was never my narrative, it was my mother's. I'm pretty sure it wasn't a realistic view of hers either.

There is also some element of this narrative that if I lost the weight, I'd have friends and be happy. I was (am) a shy individual, an introvert. My mother is an extrovert. In her story of being overweight, she talked about losing the weight because something happened in middle school that made her sick to her stomach whenever she ate so she stopped eating, she lost the weight and got friends. I believe this element of my narrative came simply from my mother retelling her story as she saw it.

It seems to me that you know the narrative that is there or elements of it at least. Perhaps rather than trying to find an instance of when your mother might have said those words, it might be more about trying to find the little things (said, done, and not said or not done) that when added together you interpreted her statements and actions in such a way that built this narrative.