Hello madam... with your history we can make out that you have concerns of hyperpigmentation on face that could mostly be Melasma...: Melasma is a hyperpigmentation patch seen on the skin and the reasons being, harmonal, uv exposure, etc... vey much common to see Melasma post pregnancy
Next Steps
Kindly consult a dermatologist and blind with pictures for better results
Health Tips
Start applying a sunscreen to avoid spread
Consult dermatologist online for further solving your concern