Hair advice!

I've noticed something today and I'm upset over it. I'm young and noticed hair loss and my hair is super thin. I've done ombré before only the ends. I have long hair. I put my hair in a high ponytail everyday for school. I do take vitamins for lack of iron and I am stressed a lot emotionally. Can you guys please oh please help a girl out and give me methods to make my hair thicker and healthier and have hairs grow back? I also blow dry my hair once a week. My hair gets pretty oily.