Hi OP, you are having a tough time!
Okay so, the doctor said it's not cancer. So it's not. It really is not cancer. You are giving in to your anxious thoughts OP. Thoughts are literally just thoughts. We think hundreds of thoughts a day and I can tell you now, most of what we think is absolute rubbish! Just because you think something does not mean it's factual, that it has any real substance.
You have to challenge your own thoughts. So you think you have cancer. Get your Sherlock Holmes hat on and investigate that thought. For it to be true, there has to be evidence right? Hard evidence. So you make a list for it being cancer and a list for it not being cancer. I can pretty much be certain that the list for it not being cancer will be much longer! The fact you have had it ten years, the fact that you must have had bloods done in pregnancy and there would be cancer markers in your bloods, the fact you have seen a doctor and the doctor said it's not. The fact you have no other symptoms. The fact you have health anxiety.
Think of it like changing rails so your train of thought is going in the right direction. You have to learn to separate the rational thoughts from the irrational thoughts.
Secondly, you need to try to understand what anxiety really is. Once upon a time, it was anxiety that saved us. It gave us the symptoms that seem so scary, to save our lives. The feeling of fear, quicker heart, tunnel type vision, wanting to run away. It's what we did in prehistoric times to get away from danger. It's a healthy thing to have. Nowadays, we don't need anxiety like we used to. We live longer, we don't have to worry something is going to eat us. So anxiety seems abnormal. It's not.
Anxiety, when there is no actual danger, is all to do with having irrational thoughts. Anxiety can not kill you. Think about behaviours that feed your anxiety and STOP them. That means googling. That means reading gruesome stories on the net, getting too involved in the news and so forth. What you put in your brain, is what it will give out. It would be hard to be anxious if say, your brain was filled with comedy films and funny cat videos no?
Also understand that because we read stories and watch things, it can seem like young people get sick all the time. This is not true. There are millions of people in the world. It is incredibly rare for a young person to become seriously ill.
Finally, if medication seems scary, why? We think nothing of taking paracetamol, antibiotics etc for physical health, but panic at taking medication for our mental health. Yet our brain is just another organ! Same as a heart or kidney or liver. Diabetics don't refuse insulin because they need it. Sometimes where mental health is concerned, we need it too.
Most people turn to the internet when they have a problem. You look on forums about antidepressants, you will read post after post from people that have had this that and the other. Then these people disappear, because their meds kick in, life goes back to normal and they don't have a problem any more.
You may not be able to control anxiety, but you can absolutely control things like avoiding anything that lowers your mood and causes you stress. You can control staying hydrated. You can control staying away from caffeine and taking a little walk each day. You can control whether you jump on Google or not. And you can control which thoughts you choose to listen to. The anxiety will go as a result.