Does ones fast break if there is blood in ones spit due to medical reasons?

AsslamuAlaikum Muftisaab
1)I have a lung problem at times there are blood stains in my spit, it is not all the time, at times I have a strange taste in my mouth when I check my spit it is a little redish and at times it looks normal. It is not blood clots only a little redish. I want to know if my fast is valid in this condition. 2)also how do I no that saliva is more than the blood and if the blood is more does that mean my fast is broken. jazakallah