Anxiety over breast examination.

I am a 20 year old woman, who a couple of days ago went to my local GP surgery due to my left breast feeling firmer and sore, compared to my right which is soft and not sore at all.
The Nurse practitioner did a breast examination and agreed that the left breast was firmer and a bit bigger than the right - but she could find no lumps, and said they looked pretty much symmetrical and ordinary.
However, she then went on to say that she would have to go out to discuss with the doctor if I should be referred to a clinic to check my left breast. I freaked out in the room, and she did her best to reassure me that lots of women have a 'fuller' breast that feels different, and that because I have no family history of breast cancer, I should not be too worried at all.
However, I have anxiety issues, whereby if something health related is 'wrong' with me, I cannot move past thinking the worst about what I could have.
She told me to come back in two weeks, after my next period where the doctor would examine my breast/s again to see if it is hormone related, but I am not sure if it is, as my left breast has felt fuller and...'present' for years. The pain is by no means unbearable, and I would even hesitate to call it a pain really, more of an ache or pressure.
I broke down outside the surgery and my mum called the surgery later for further reassurance and information, in which the nurse said that if she was concerned, she would have referred me on the day, and that is a perfectly normal routine for women to come back after their next period for further examination.
I am terrified of Breast Cancer, and these two weeks are playing havoc with my nerves.
Does it sound like I should be concerned or worried?

Hi Scarlet - I'm not a medical doctor so I can't diagnose what is wrong with you but I can say speaking from experience that you really shouldn't be concerned.

I had a similar problem a couple of years ago but I did have a lump... a big one. The doctor wasn't concerned & knew what it was but it is routine for anybody with a breast issue to be referred to a breast clinic. The fact you haven't been and they have told you to come back after your next period suggest it is hormonal. If they had serious concerns you would have been referred immediately. You also say your breast has been 'fuller' for years. That's just the way it is. No woman is symmetrical. If it was something serious you would be a very poorly lady by now. Try not to worry hun. It will be ok. Big hugs. xx

My ex wife had many lumps and when referred it was put down to a simple hormonal issue. Many women have irregular sized breasts, it's just one of lifes things x

Thank you so much for your replies - it really has made me feel a bit better about the whole thing.
By 'fuller', I mean that I have been feeling the pressure in my left breast for a few years. Is that normal and okay too? I never really checked my breasts before now, but recently have been checking out of fear that I have a lump or discolouration, so I cannot really say to the doctor if they have changed recently or not. I also have never really noted or followed if my breasts change before my period either, so again I am rather useless at being helpful in that circumstance.
Looking in a mirror, my left breast is barely recognisably bigger at all, besides it looking a bit wider. But the muscle or maybe tissue does feel harder and bigger, and is more tender to touch than the right, but again the nurse said she could not find any lumps and my lymph nodes were fine.
Thank you both again!