I have a problem regarding Ramadan and fasting. Actually I suffer from irregular menstrual cycles. Today, During fasting, I saw some little dark blood, and I cannot determine if it’s haidh or istihaza, because of the irregularity of blood appearing. As in, sometimes I would see blood, but on the same day after few hours I would not see anymore blood.
In this case what should I do? should I consider this as, Haidh or istihaza?

generally speaking a blood is only considered Haidh if it flows for three days without any big interruptions in the flow.
If there were big time interruptions then it will be considered istihaadha.
Besides that irregular menses starts with the flow of blood that has characteristics of Haidh blood. And flows for a minimum of three days continuously.

I have a problem regarding Ramadan and fasting. Actually I suffer from irregular menstrual cycles. Today, During fasting, I saw some little dark blood, and I cannot determine if it’s haidh or istihaza, because of the irregularity of blood appearing. Meaning one day I will see little blood, and on the same day, after few hours there will be no blood.

In this case what should I do? should I consider this as, Haidh or istihaza?

This is not Haidh but rather Istihaza. You will go by the ruling of Istikhaza and continue with your prayers and fasting until the blood comes and continues the way it normally comes. That’s the time you will consider haidh. For now, it’s not Haidh.