Well, unfortunately if there is pain and itching, then you will need prescription medicines . A thorough examination of your scalp is needed to assess and rule out bacterial infection along with the lice infestation. And prescription medicines are the only medicines that will give you quick relief. Which unfortunately can't be given on a chat without physical examination.
Next Steps
Visit an allopathic dermatologist near you immediately please. And before you choose your dermatologist read this link please : http://www.skinmatra.com/single-post/2016/07/03/Skin-Troubles-Here-is-WHAT-NOT-TO-DO
Health Tips
Do not self medicate at all. The tendency is to 'try ' different shampoos. Please don't. You will only be wasting time .