What Causes Recurring Lump At The Back Of My Head With Headaches?

when I get a headache a lump appears on the back of my head, I also get dizzy, feel sick and have pins and needles in my right leg. This lump disappears when my headache is gone. The headache can last all night and the lump is very prominent when touched - so much so my sister thought I had banged my head. The doctor has dismissed it but I am concerned.