One thing that can cause itchy skin is allergies or an allergic reaction to something. One easy way to check is to take antihistamines for a couple of days if you're able to. Perhaps check with a pharmacist to find one that doesn't clash with any meds you are on.
Have you changed your laundry soap or laundry softeners or other household cleaners lately? Laundry softeners are notorious for causing skin reactions (at least in my family). All my laundry products are for sensitive skin, so lack fragrances, dyes etc.
Also, think of any other new products such as skin lotion, soap, shampoo etc that you started using before the itching started.

The product that made me miserable for six months was Mr Clean.