The data you reported (constantly bleeding for 72 days after stop taking Mycroginon 30 because of no menstrual periods at all) might indicate that you experience hormonal imbalance. Hormonal imbalance is not uncommon in women that take hormone containing birth control pills (BCP). Hormonal blood levels are expected to be changed when taking BCP, but in certain pattern depending on the substance. In some women, the hormonal blood levels are not changed as expected. Withdrawal bleeding is expected after stop taking birth control pills because of the thick endometrium (inner lining of the uterus) that has to be expelled, but it should not last that long as you reported (72 days).
You might want to visit your gynecologist for hormonal laboratory tests which might reveal the hormonal imbalance. Physical examination is highly likely to be needed in order to rule out other conditions which might have caused the continuous bleeding (cervical polyps, uterine fibroids etc.). The bleeding is different in these conditions, but the amount of blood lost was not provided. The presence of PCOS might additionally affect the ovaries and their hormone production.
If hormonal imbalance is detected you gynecologist might suggest taking some hormone containing BCP to try to restore the regular hormonal production.