Boring story but made me feel awkward

Im very socially anxious, but try to involve myself. Literally today in the middle of math class, holding my computer with a jumpscare video loaded, I approached a classmate. I asked her "hey do you see anything here?" she said no because it was a black screen. Thing is, I had pressed play too early, and she didn't even get startled. So she just looked at me like "._." I got so embarrassed that I ran away cheeks all red, and accidentally sat in another girl's seat while she was away for the toilet. I only realized after she came back, and LITERALLY SAT ON MY SPOT.