Good day , what would be causes of not ovulating and irregular periods (ultrasound all clear and healthy of ovaries and uterus)?

Irregular ovulation: is very common in females and has several possible causes. A few of the more common reasons are polycystic ovarian syndrome and congenital adrenal hyperplasia. You need a complete history, physical, and appropriate tests to make diagnosis. Hope this helps!

Many causes: There are many potential causes, including certain medical problems, excessive weight gain or loss, or other types of hormonal imbalance. It's important to evaluate, see your doctor.