i found a lump under my tongue two weeks ago , its growing and growing by the day my doctor said they don’t know what it is i have been to numerous appointments but stull nothing ,

at first it was just the size of an ulcer then it was the size of a 5 pence piece it was clear , then it went white and soft now its going very hard and full of blood ( it is on my vein and its so sore) i have never felt pain like it , since no body knows what it could be i was wondering if you could help me out and give me some advice on what to do and how to go about it , with me being 18 and rather healthy it is very strange for them to not know weather it is cancerous or not