Small lump in back of head

Hi All
First post on here!
I have found a little lump at the back of my head just under and to the right of my left ear, it goes up and down all the time but typical me is now thinking its something to worry about! now before anyone says go to the Dr's I did, 5 years ago now and was just told that it is a gland and I may need to go back to have it drained if it gets to big.

I have no idea why I am now concerned about it and like I said I touch it one minute and its the size of a pea then say 10 mins later I can hardly feel it!

Its not getting bigger nor do I have any other symptoms at all, do I just ignore it or do I go back to the Dr's?