Sudden Hair Loss

ok, I stayed inside my house and did not go outside much for a year and then when i got into college I started going to out a lot suddenly. Suddenly my hair started falling out. My scalp is oily and i cant go without shampooing for a couple days because of the oil build up. I also have a severe case of dandruff. I tried practically all the dandruff treatment there is, form herbal to OTC treatment to natural treatments. U name it, Head & Shoulders. Nizoral. Tea Tree oil. Lemon Juice. Apple Cider Vinegar. Selsun Blue. Coal Tar. Pine tar. Coconut oil, Amla oil. Olive Oil. Tea tree shampoos. Castor Oil. Jojoba oil. Tried taking mulivitamin supplements and biotin.Yes I have tried all these with no luck neither in controlling dandruff or hair loss. I do not think I have seborrheic dermatitis or any other skin condition as the products would treat the disease if that was the case. I do have digestive issues and my stomach gets upset pretty easily. However this is a new thing as I moved to the US recently. But my hair fall started long back. What might be the case? Any suggestions will be greatly appreciated, thanx in advance.