An update on this. I applied for funding to see about removal and was denied due to my issue not being 'clinically exceptional compared to other patients'.

I was told to "wait and see" as fibroadenomas can reduce in size, and to go back to the doctors in 12 months, unless there is a sudden change. Since my last doctor's appointment (beginning of the month) it has grown again and has made wearing a bra painful due to the position of the lump.

I kind of feel like I've been told to ignore it and to stop bothering them.

Hi, sorry to hear that you’re having such a hard time! 
i just thought I would share my current experience with my fibroadenomas to maybe help. 

so a couple of years ago I went to the doctors about a little lump and was told that it’s probably a fibroadenoma and was referred to the clinic. At the clinic they found another area that wasn’t yet a lump but I think they said it was a dense area. Anyways they did an ultrasound and the original lump was confirmed as a fibroadenoma however the dense area looked a little concerning so they did a biopsy (I’m 21 and was 1 18-19 at the time). After waiting ages for the results it came back that the dense area was also a fibroadenoma and no further action needed.

after about a month I noticed that  the dense area that was biopsied had now grown into a lump. it continued to grow so I went back to my gp. She said that she could feel quite a few lumps so was sent back to the clinic. At the clinic I had another ultrasound and they told me that I had 6 fibroadenomas 4 of which were overlapping. They said that when they are overlapping they measure them together and I think I was measuring at just under 4cm, they said that they won’t consider removing them until they get to 5cm. 

I’m now 21  the lump has continued to grow slowly however in the last year it’s had quite the growth spurt I can cup the lump with my whole hand. But I also have really bad anxiety which is preventing me from going back to the doctors I feel that because it has been confirmed to be a fibroadenoma they will think I am paranoid for returning due to the increase in size but it’s getting to the point where it feels like it will just keep growing and growing but because I wasn’t advised that I should come back if it grows I am too scared to go in about it.

any ways one of my fibroadenomas were biopsied and they are still growing I don’t know if that helps ease your mind at all. I know that fibroadenomas can grow and that there is such thing as giant fibroadenomas so please know that the fact that it’s growing doesn’t ultimately mean that it’s something more sinister. However I completely understand that it can be really hard when you have a lump that is continuously growing or changing. It’s very confusing because you are always told to go to your gp for any breast changes but when you have a fibroadenoma that continues to grow they are always changing and it can be difficult to know when or if you should be getting seen again. 

my advice to you would be to push for a biopsy if you are super worried. you should be able to have some peace of mind and your age shouldn’t be a reason not to give you that. I hope that you get the answers you need :)