Hard Lump on the Back of Neck

Hey Guys, 

So I’ve reached a point where I literally cannot stop thinking/worrying about this lump on the back of my neck. It’s on my hair line to the left of the back of my neck. It’s a hard, non-moveable lump that feels around 2-3cm diameter. I rarely self-diagnose because I know how horrifying Dr. Google can be, but since I’ve already lost someone to cancer, every hard lump is a bit of a red flag. I’ve suddenly also started getting really bad migraines which make me feel so dizzy, am constantly tired with joint and muscle aches, and I have both back pains (lower back and sometimes around shoulder blades) and a super intense chest pain that comes and goes (particularly when I drink gin, which is unfortunate to say the least!). I’m also struggling quite a bit to breathe recently - it just feels like my chest is constantly tight with some relatively infrequent coughing.

I have been to the GP who just believed that it’s a lymph node that’s naturally sticking out a bit (which is what I originally thought anyway), but it’s now been a week and it seems to be getting bigger (I was also wondering if lymph nodes in their natural state should be solid and non-moveable?). I was given a PPI and sent on my way (to deal with the chest pains). I’m presenting barely any classic infection symptoms which initially got me worried; so naturally my worryful mind immediately thought it could be the worst case scenario. 

I’ve seen many posts here about the same kind of issue, but I was wondering if back pains, migraines and chest pains/breathlessness have any connections to neck lumps with regards to those who have been through the process. 

Thanks so much!