Delayed periods along with clots and heavy pain usually point to a hormonal or anovulatory cycle, where the uterine lining builds up more than usual before shedding. Stress, PCOS and
thyroid imbalance are common triggers. The weakness you're feeling could mean the bleeding has brought your haemoglobin down a bit.
Next Steps
Get a haemoglobin and
thyroid check done, along with a pelvic ultrasound to look at your ovaries and uterine lining. Eating iron-rich foods and resting through the heavy days will help with the weakness meanwhile.
Health Tips
See a gynaecologist soon if the bleeding soaks through a pad every hour, or if the weakness turns into dizziness or fainting.