Is it normal lately when i'm stressed i feel the need to scratch my legs?

Although most of my exams are over, I still have a couple more to go, and this habit of mine is causing me problems when I try to study. Since the exam season started, whenever I study, I keep feeling the need to scratch constantly at my legs. I've sort of had this problem before but only when I was really stressed out and, even then, it wasn't this bad.

It's not that they're itchy or anything. It just feels nice when I scratch them, for some reason, and I find it hard to stop myself doing it when I'm trying to study for that reason. My nails are pretty short, so they don't do that much damage, but as of late I scratch them so much (since I need to do a lot of studying) there's always red marks on my legs and they're pretty sore. I shave too which I think makes it a bit worse for my skin.

IIN? Any advice to quit the habit?