No, you are most definitely NOT fat. You are thin. I have no idea how much you might weigh, but normal weight for someone of your height is 5' 4" is110-145 pounds. I would think you would be on the lower end of that. But if you're not, don't worry about it.
If you think you might be fat, you may have a body image disorder and you might want to seek out counseling or some other services for this.
When I was young I was normal weight, 128 pounds, 5'6", but most girls in my high school and then college seemed skinnier than me. When I looked back at pictures, I was a little bigger than other girls, but I was perfectly normal weight, on the thin side. It's all about perception.
Now due to some medical treatments I have gained weight and I would love to be back at that weight.
Anyway, you are not really not fat and I'm sure you're not overweight.
You might want to post your age because people are worried about child porn. I would guess you are of age because that looks like a college dorm room. And it's not really a pornographic image, in my mind, but I'm certainly NOT an expert in that area!