Hi all! Sorry if this is slightly long to read.

I'm 21, and female. In november, I noticed one of my lymph nodes in my neck was enlarged, without any other signs of illness. Shortly after my groin swelled up, and then I noticed another in my neck was enlarged too. The groin 'swelling' seemed to go down, I occasionally worried about the ones in my neck, but didn't do anything about it. Since november, I have been getting increasingly tired, however this comes and goes. Some days I am fine, other days I am exhausted, and it is completely unrelated to how much sleep i've got! One in particular on my neck seemed to be growing larger, and I then noticed I could actually still feel the one in my groin. I've also seemed to have slightly tender side of my breast, on one particular side, which comes and goes too. I don't know if this is related.

I finally went to my GP on monday, and she examined me and found some more  - another in my neck, one above my collar bone, and another in the other side of my groin. So in total I have 6, that I know of. I'm also convinced another one has swelled up in my armpit since I saw her, but I don't know if this is stress related? The day it felt swollen, the side of my breast on that side was also tender to touch (the opposite to where it has previously been sore). I've also seemed to have developed a 'tight chest' feeling and a chesty cough when I breathe in deeply since seeing her, after she pressed down on my stomach and told me to inhale/exhale, but then again, maybe its always been there/ is stress related? I'm just noticing it now?
I had a chest x-ray this morning, have a CT scan on my neck in just under 2 weeks, and blood tests in about 3 weeks. I feel a bit confused to be honest, I know they're testing 'to rule out' cancer, but what does this actually mean? a specific type of cancer? any cancer? I don't really understand the stages of diagnosis, and how likely really is this to be cancer? I don't think I've had any significant weight loss, and I definitely have not had night sweats to the point I've drenched the sheets, i've woken up hotter than usual some nights but that could be a whole range of things.

 I know lymphoma can cause enlarged lymph nodes - does anyone know if 6 palpable nodes is a bad sign? The one in my neck that I had originally noticed seems to feel quite hard and doesn't move, but my GP did say the ones in my groin area are movable and so that is more 'promising'. I'm trying to stay positive but the worry is really eating away at me, at a time where i'm trying to write my university dissertation too!

Any kind of insight/opinion would be really helpful/appreciated, its driving me crazy!

EDIT: I also had glandular fever 2 years ago, so we know it isn't this.