First of all, I am so sorry to hear about your mother. That had to be so hard for you to deal with. It would be for anyone. It's understandable that you are now worried that you have what your mother had. The knowledge about cancer at such a young age without anyone explaining it caused you to fixate on it.

I think you should see a doctor to check into the symptoms you have that are making you worry. What could the doctor tell you that could possibly worse than what you are telling yourself? You say "I have lung cancer" when you only have told yourself that. No doctor has told you that. You say you can feel it spreading to the point when an infection in your tooth is just more evidence of it.

This is not normal. You shouldn't have to live like this. Go to a doctor and get a regular physical. If there is something wrong, if a doctor does a real diagnosis, then it can be treated. All that is happening now is that you are worrying yourself sick. You worry that life will never be the same, but it sounds like things are already bad enough. You need to take a chance at making things better.

You also should consider talking to a therapist or someone about your hypochondria. This is seriously disrupting your life. There are reasons why you think this way and why you worry so much. There are also treatments for it. Wouldn't it be nice to not have to worry about all of this and just be able to live the life of a normal 28-year-old? People could reassure you all day, you could have every test in the book come out clean, but it wouldn't eliminate the worry. Please consider getting help for this. I really think you will be glad you did and you will feel better sooner than you ever thought possible.

I wish you all the best.