I used to have episodes of really uncomfortable burping. They went away after I had my gall bladder removed.
Now, if I eat too much fatty food, I get the same symptoms (burping, gas, discomfort, bloating). I try to regulate how much fat I eat at a time. If I overindulge and get "the burps", then I take an OTC anti-gas pill (simethicone– spelling?), and it subsides.
I have had a number of "cancer scares" in my life. Please don't panic about cancer. : ) A lot of symptoms of cancer are also symptoms of other, less serious, problems, especially in the guts, which can be really complicated– or really simple (too much fatty food).
If you are worried, see a doctor. If the doctor doesn't seem to be listening to you, get a second opinion or even a third. Try to find a doctor that you trust, one who listens carefully. Medicine is still an art as well as a science. At some point, you just have to trust the scans and the doctors…But you can still be in the "watchful waiting" stage.
Once, a gyn literally laughed out loud at my cancer fear. She was right, it wasn't cancer. But I never went back to her. I now have a great gyn, who sees things from my perspective: There are reasons for my concern but I'm not a doctor, so she explains things to reassure me, and she doesn't laugh at me.
I don't mean to minimize your worry or to make any of this seem easy: It's hard to get the right "tone" in a short post. It IS scary when your body is doing strange things, and sometimes it does seem that the doctors aren't hearing you.
I have really rambled all over the place in this post- sorry about that! But I hope that sharing some of my experiences has been helpful to you.