hello. i can appreciate your concern. usually even if we are taking adequate food intake, our modern day diets are deficient in nutritional value. Also as you are breastfeeding, you have increased calcium demand- 1200 mg per day. And vitamin D is essential for absorption of calcium from gut,its deposition in bones, and helps reduce its excretion from kidneys. You need to have vit D levels above 30 miu. And recommended daily intake of Vit D is 1000 iu. So you can take Vitamin D3 (60,000) once a week for 4 weeks,with gap of 4 weeks and again for 4 weeks. please continue Calcium supplements till you are breastfeeding. Also i will insist you to include calcium rich foods in diet- like green leafy vegetables,low fat milk and milk products. Also i will encourage you to adopt weight bearing exercises like walk,jog,run and light resistance training; this will help strengthen bones. Thanks