What Causes A Lump Behind The Ear, Blurred Vision And Dizziness?

Hi, I am 25 years old.. Iv been to Drs over a year now about a hard lump behind my ear.. I get told different things,, one dr said it was my mastoid bone, two des recently told me it was my lymph node, behind my left ear.. I was put on anti biotics and then another dr told me I never needed to be on them because they didn t think my lump was that bad and I was having reaction to the tablets,, I have recently noticed that the lump swells really big when tiered and when I have woken up.. Have u any idea what it could be? As It doesn t feel right and I have a past of seeing double and feeling dizzy but I feel as though the Drs aren t listening to me and think I m over reacting .. Thank you