Is it normal that i still suck my thumb while rubbing silk?

I'm 18 and I can't sleep without this specific red silk pillowcase. I take it with me everywhere I know I'll be sleeping. I never put it on a pillow, I hold it like a blankey. I like to suck my left thumb and hold the pillowcase in the same hand while I do it. I'll fold it between my fingers and rub the pillowcase against my lip and the underside of my nose. Sometimes I'll rub the pillowcase over my eyes and against my cheeks. I'll also rub it between my hand and my forearm and against my stomach or chest. I just love the feeling of the case against my skin, escpecially my face. I'll fold it two or three times between two fingers and slide it between them in a snapping motion...I like the feeling and sound of it when I do that. It calms me down and comforts me. It takes me a long time to fall asleep without it and I'll feel anxious the whole night if it's not with me.