Hi During pregnancy- because of hormonal influences- all the ligaments and joints would have become lax. After child birth, when they return back to normalcy, aches and pains can happen. Hope you had your Calcium and vitamin supplements through out pregnancy and now you are continuing with your calcium supplements. If not please do take them along with vitamin D after consulting your doctor. While you are feeding- you need extra calories and protein- Else your body will get burnt for producing milk resulting in all deficiencies. This will result in early stoppage of breast milk production too. Till 6 months of age, exclusive breast feeding is the best for your baby. Please take care of diet (Include lot of fresh fruits, vegetables, nuts, milk, eggs) and take adequate rest and resume feeding your baby. Please approach your Obstetrician who will advise spinal exercises for your back pain. If needed you can get physiotherapy done too. And mild pain killers that are safe while feeding can be used under your doctor`s advice. A look into your Vitamin D status will be of help. Hope my answer helps you. Wish you and your baby good health.