I had a lump in my neck about six years ago. It is still there has grown slowly  it is on my left side slightly Right of my clavicle I can move it slightly. It is probably the size of a marble it doesnt feel like its connected to anything as if its between my neck and my skin
HI. By the position you have mentioned and the duration - this looks to be a solitary nodule of the thyroid gland. Get this confirmed by ultrasonography and go for an FNAC to get the right diagnosis. Even a good clinical examination by a Good Doctor can give you a diagnosis. Also go for the blood tests particularly thyroid function tests. You may need removal for the histological diagnosis to rule out a sinister problem.