Hi, the past few months, every now and then I wake up with golf ball size lumps on the back of my head. Give it three hours and there gone, there always on the right hand side of my head behind my ear. ( in that general area) but the last couple have been hurting. I can push it around maybe 1cm in all directions, the last one I had, I kept pushing downwards and managed to get rid of it. Have you any suggestions on what it is?