Long gaps between periods followed by bleeding that won't stop for months usually points to a hormonal imbalance, not a dangerous disease. The heavy flow and pain these last few days are part of the same pattern. The mild dizziness you're feeling now can happen when periods run heavy for a long time and affect your blood count.
Next Steps
A blood test for hemoglobin and a pelvic ultrasound are the usual first steps. A gynaecologist can also prescribe medicine to stop the current bleeding sooner, so please don't delay out of fear. These problems are common and treatable, and an early visit prevents them from getting worse.
Health Tips
See a gynaecologist soon, and go in urgently if the dizziness worsens, you feel faint, or the bleeding becomes very heavy.