It sounds like your cat has vestibular disease. This is when the inner ear and brain do not communicate and it throws the cat off balance. An inner ear infection can cause this or sometimes it is idiopathic , meaning there is no known cause. I would bring the vet in for examination of the ears and to check for a thiamine deficiency. If this is idiopathic then it will subside in a few weeks.
Here is more on this: http://www.petplace.com/cats/vestibular-disease-in-cats/page1.aspx
Vestibular disease would not cause a lump, if the lump is soft and fluid filled then you may be dealing with an infection, if the lump is fastened to the tissue underneath then it is more serious. I would take the cat in to have the lump examined. The vomiting could be from an infection or from being dizzy. You may have more than one thing going on here. You said it happened before, what was the outcome? Did you seek Vet help?