As someone has mentioned above, stress does contribute to hair loss but that's not the only factor. It could also be due to poor diet, lack of nutrition (same thing as poor diet), and even the chemicals you are using for your hair. I personally recommend taking a vitamin supplement for hair, skin, and nails, which could be found at your local drugstore or even Walmart. Okay, now you're thinking "Is there an alternative to vitamin supplements?" Pills are not for me. Well, fortunately there is an alternative and that is adapting a healthy diet and lifestyle. "What you eat is what you are". In this case, foods such as almonds or anything containing biotin are essential for hair, skin, and nails.
Shampoos, conditioners, and sprays may also affect your hair and scalp. If you have oily, thin hair, I suggest a shampoo that boosts the volume of your hair. A really good but pricey product that falls into this category but proves to be highly effective is Paul Mitchell Extra Body shampoo and conditioner. Normally, Paul Mitchell products are not sold in drugstores or just any local store. However, you may find them at a local hair salon and for consumers' convenience, they are most always likely bundled together for around $20-$30. Walmart wise, Herbal Essences Volumizing shampoo and conditioner (the orange bottles) are also great products. You may also find them at other stores equivalent to Walmart. They not only help your hair but it also smells incredibly good!
Last but not least, DO NOT SHAMPOO AND CONDITION YOUR HAIR EVERYDAY. Doing so will strip your scalp of natural oils and dry out your hair. I recommend shampooing/conditioning every other day for healthy results.