Anything To Worry About Swelling In The Neck Under The Chin ?

I am 31, 5' 4" and about 12 stone. for 4 months I have had a swelling in my neck under my chin. I was referred to a heamatologist, who was dismissive before he examined me, which wasn't very encouraging.
I tend to power on however I feel - I don't moan unless I feel really poorly. and I have gone from tired, to achey, to run-down, to now when I feel exhausted if I stand for a while over those 4 months. I also have a vertigo sensation when I slightly incline my head often, and feel quite severely nauseous at least 1-2 times a week. I have improved my diet, reduced smoking and alcohol alot, and if anything I feel more tired. I had extensive blood tests, which all came back normal. I was silly last time I saw the dr - I didn't want to worry anymore, so I attributed my current symptoms to a cold and said I felt better. Family have again and again reminded me how much I have said I feel tired and exhausted despite adequate sleep, and the lump in my neck has not gone (I used the term throat to mean both to my dr, and told him that the sensation of a lump had lessened, which only afterwards I realised was misleading). Should I be worried? I don't want to worry. But I have a baby and a 6 year old, so I can't be too blaze as leaving them is unthinkable.