1. because depression
started after the birth of son,(Postpartum depression-PPD) it can be presumed that it was not the side effect of chemotherapy
2. you haven't mentioned about the symptoms arising from depression neither about the changing intensity?? (frequency,intervals,symptom free periods)
3. any feeling of suicidal thoughts or tendency, change in mood, any feeling of hopelessness, worthlessness and helplessness??
4. Age is a risk factor for PPD, i.e. the younger you are,the higher the risk, so it could be one of the reason.
5. any marital conflict or lack of social support?
6. avoid alcohol,caffeine,pungent,hot and spicy food, do not isolate yourself,keep in touch with your family-friends-relatives, don't try to be perfect at all the times,keep yourself busy in accordance with your capacity and ability for work,.
7. Ayurveda relaxation Techniques
like Pranayama (bhastrika and kapalbhati) are beneficial alongwith bhujangasan,shavasan,sarvangasan, and vakrasan.
8. drinking lemon juice with sugar in a glass of water releases stress
removing hormones, thus bringing mind at ease.
9. consult with a Psychopath and Ayurveda Physician about the same.