Your biological clock has been disturbed. 3-4 hrs sleep may cause headache. But not in each and every case. There may be some other causes for headache.
You are already on thyronorm, which suggest
thyroid gland disturbance. Thyroid gland disturbance may affect the sleep.
Next Steps
Consult with general physician/ psychiatrist/ clinical psychologist/ homoeopathy.
Health Tips
Thyronorm dose may be revised.
Revise your daily routine.
Don't sleep in day time.
Try to solve the problem/reason for the sleeplessness rather than take long sedatives for sleep.