Haven't had solid bowl movement more then 8 months pain & feel mass upper abdomen weight gain dad has colon cancer & aunt has stomach cancer worried?

Don't think cancer: Do think of having a good examination and solid efforts to treat whatever is the cause. Follow the dietary and behavioral recommendations that result and reassure yourself that it is not cancer. This may involve psychotherapy aimed at health anxiety issues. Take it step by step - start with a good GI exam. Good luck.

Lots of issues...: You're describing many systemic concerns, but its impossible to tell here if your symptoms are all due to organic/metabolic disease or even related. Granted, your family history is notable, ; may indicate lynch syndrome. A thorough history ; physical with some simple investigatory lab studies ; x-rays would be a great place to start in getting the answers, reassurance ;/or treatment you need.