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Lot of women expericne backache
after C section. Could be due to epidural. Or due to prolonged sitting for nursing the baby, or due to weight gain.
You can take homoeoapthic remedy HYPERICUM 1 M * one dose only, I have given it successfully for backache following C section, even if its been for years.
Weakness and triedness can be due to, loss of sleep/ over work/ improper nutrition.
Also you can get your Thyroid
hormones checked as well.
Exercise is useful for both of your problems. Also some yog aasans are helpful ( do under supervision only).
Once you stop breatfeeding, menes wil become regular.