Looks like you are feeding your baby without supporting the small of your back or you are missing
calcium supplements
Next Steps
Take TENS for low back ache at home with the help of Home TENS device like BLUEIDEA MESIN Terapi Digital
Health Tips
Continue iron and
calcium supplements
Mothers Horlicks two spoons with milk two times a day for a month
Correct ergonomics while breast feeding
If TENS not possible at home get a physiotherapy visit for Interferential Therapy(IFT)