Honey, you have anxiety and Obsessive Compulsive Disorder (OCD) - and you are very prone to worrying about things. This is not the first time you've been sure you had stomach cancer. You didn't have it then.
So facts:
Stomach cancer is the 15th most common cancer. Which is to say not common at all. Compared to other cancers, it is relatively rare, making up only 1.5% of all cancer cases. It's most often diagnosed in people over 55, the median age being 69. Average age of people dying from it is 72. It is twice as often diagnosed in men than women. The number of people dying from it in a year is about 10,730 - when you consider that there are 319 MILLION people in the United States each year, that is less than .000003%...a tiny, tiny amount of people. In contrast, more than SIXTY times that many die from heart disease!
It is HIGHLY unlikely you have anything serious.
Weight fluctuates. It happens for very little reason. Don't panic.