:wasalamex
I understand you wish to take the black seed because of the hadith that it is a cure for all diseases, and this is all very well. But there are also other things along with that which you need to do to make the black seed fully effective, such as getting to the root cause of your health problems and removing the harm (carcinogens, free radicals etc), exchanging the faulty diet for a good diet, following the principles of health according to the Prophets Medicine. And in your particular case where u have been through chemotherapy, it is very important for u you see a good nutritional therapist who can properly support your body in getting rid of the after-effects/toxins of chemotherapy which is causing havoc in your system. You need a proper protocol /dietary /nutritional / detox plan, please see my PM for contact details to a practitioner who specialises in this field.
Then you can add in the black seed and be advised on how to take it in the correct ratio which makes it Al-Shifaa (The cure). You may also consider looking into Hijama for getting rid of toxic blood/immediate relief.
May Allaah :arabic2: grant you complete recovery and health. Aameen.