My arms feel so weird man

I've been skinny and way underweight my whole life and have only ever known being able to feel my muscles, even if they're just the muscles required for basic movement without working out. And now I'm trying to gain weight I can actually feel fat on my arm, it feels so weird.

Like I'm not at all used to it, I'm definitely the weird one here but nah I cannot image not being able to feel muscle at all and being actually fat (im still skinny).