Since my period is irregular, and the bleeding continued for more than 15 days in Sha'ban, do I have to make up the days I fasted and prayed after Ramadan, and is it permissible for me to perform Umrah while this irregular bleeding continues?

If the blood flow exceeds 15 days and nights, the woman experiencing it is considered to have istiḥāḍah (non-menstrual vaginal bleeding). She must take precautions by tightening a cloth, perform ablution (wuḍūʾ) for every prayer after its time has begun, and her fasting is valid. If she has a previous habit (a regular menstrual cycle), then what aligns with it is menstruation (ḥayḍ), and what exceeds it is istiḥāḍah. If she does not have a habit but can distinguish menstrual blood by its characteristics, then what she distinguishes as such is menstruation, and any excess is istiḥāḍah. If she has neither a habit nor the ability to distinguish, then 6 or 7 days are considered menstruation, and anything beyond that is istiḥāḍah. She only needs to make up for the days she missed fasting, assuming she was menstruating, and she must make up the prayers she missed after her menstrual period ended, before she realized she had istiḥāḍah.