الجواب وبالله التوفيق

A person who is sick to the extent that he (or she) can’t fast or it is evident that by fasting his state will deteriorate further then it is permissible for him to not fast. It is mandatory on him to perform qadha for such fasts when he becomes healthy.

Therefore due to the condition you have mentioned in your question, do not fast and perform qadhaonce you become better through the treatment you are receiving.

(قال تعالی فمن کان منکم مریضا او علی سفر فعدۃ من ایام اخر (القرآن، سورہ بقرہ

(ومن کان مریضا فی رمضان فخاف ان صام ازداد مرضہ افطر و قضی (کتاب النواذل، ص400، ج6 بحوالہ ہدایہ

واللہ اعلم  بالصواب