Hi Christoph
This message may be late...
You must be quite worried. The best thing to do is get it checked. It is quite normal to worry about what people think. My parents had cancer a few years ago and this made me anxious that I might get it too.
I worried that my doctor thought I was becoming a hypochondriac. However, I wasn't going to take any chances. A while ago I noticed a lump under my arm. I've always had fatty lumps on my arms and legs, so the doctor thought it was just this.
However, I thought the lump under my arm was getting bigger. The doc still thought it was nothing but asked me if I wanted to get it checked out since I was obviously worried. I said "yes" because I didn't want to find out months later that I had a a serious problem.
The lump was removed and checked. Guess what? I have Hodgkins Disease.
It doesn't sound like you are a guy who is unduly anxious. You exaggerate, sure... your family may know that, but your doctor doesn't, so talk to him about it. Hodgkins is quite common in young people and I am sure he will take the lumps seriously.
If the lumps are getting bigger, check it out fast.
Joey