What Causes Painful Neck Swelling, Constipation, Difficulty In Swallowing And Nausea?

Hi, I am now 19 and since 3rd year the bottom of my neck swells out, but only sometimes, some days being worse than others. There isn t a lot of pain sometimes there isn t any at all... Sometime when I swallow food it goes down really slowly. I also get constipation, really sore muscles, head aches, nausea, dizziness and can find it hard to sleep at night. I ve been for Ultra sounds I ve got a little cyst and my thyroid is fine and so is my blood tests. I need help. Its getting me depressed. Some days are easier than others. Thanks Nicola