What Causes Hair Loss, Headaches And Constipation?

My hair has been falling out A LOT recently. Not just a few strand, but loads. My pillows are covered in the morning, my hairbrush filled after brushing, my hands flooded in the shower... I've been gaining a bit of weight recently and have had BAD constipation problems. I've been taking 3 laxatives a day for the past four days and nothing has happened. I have not "gone" in over a week and for the past two months or so, when I have, they have been very little. My mood has been off (depression, tired, bored) and I have been getting headaches often. Is this something to worry about? Is any of this related? Before making an appointment with a doctor, are there any supplements that may help me? Am I lacking any vitamins in my diet?