You are experiencing PICA which results when there is mineral deficiency, so your body is making you crave clay during the time of your menses. Your menses must be heavy, and you're losing a lot of nutrition (minerals) in your menstrual blood. Recommended Dherbs.com products include: Menstrual Cycle, Female Hormonal, and Vitamin & Minerals OR Electric Greens Combo (or both formulas).
Electric Greens Combo
Female Hormonal
Menstrual Cycle Formula
Multi-Vitamins and Minerals