Why do I feel guilty when people talk about what I ate?

When ever people comment on what I ate I always feel self conscious and guilty. I feel like a shouldn't have eaten in the first place. For example, I live with my aunt and uncle and the other day my aunt made spaghetti at around noon because she was going to come home too late to make dinner. I had woken up at around 8 am, but I waited until 2 in the afternoon to eat even though I was really hungry. The reason I waited was because I didn't want to get food in front of my aunt and cousin, who were getting ready to leave anyway. When they left, I waited another 30 minutes to go to the kitchen. When I finally did get something to eat, I got 2 microwavable burritos and a small side of spaghetti. The whole time I was making my plate I was extremely quiet because I didn't want my other cousin (who was in the next room) to notice what I was putting on my plate. I know the food wasn't off limits or anything but I still acted like a was smuggling something illegal. I felt ashamed. After my aunt came home, my uncle and aunt were talking about who opened the burrito bag in the freezer. When I came up from the basement, my aunt asked if I had burritos for lunch, and I told her that I did (I didn't mention the spaghetti I had with it). But when I was walking to my room, I heard my cousin say that I also had spaghetti. This made me feel so guilty and I felt like I had been caught for committing a crime. I know it wasn't a big deal, but it was to me for some reason. That was the only meal I ate throughout the day, but I felt like I had consumed everything in the house, after everyone finished talking about what I ate. And I couldn't stop thinking that they were all judging me and that they probably thought that I was being fat. And for the rest of the night, I was terrified that I was going to get hungry again and to this day I still feel extremely embarrassed and guilty for eating even though I only ate once that day. And even when my aunt makes our plates for us, I still feel guilty for eating food. Also, it's not like I'm the biggest person in my family. I am over weight, but my aunt, cousin and uncle are all much bigger than me. And please don't tell me that I need to stop eating so much because I already know that. I really just want to understand exactly why I feel so guilty when people either talk about or know how much I ate.