I need help writing a pay raise letter

I work at a Medical Spa. I have been there 4 years and I have never asked or received a raise. My position is A Aesthetic Consultant. My duties include .. Answer phones and schedule appointments, I prepare charts for clients that are coming in, I do laundry when needed. I am the only employee doing Coolsculpting which I come on my days off to accommodate the client, I also work after hours. I am loyal and a hard worker. I am also doing Bodytone now while running the front desk and doing coolsculpting.