Hello! Thank you for the query. Weight lost is always a symptom that should not be neglected. Almost all cancers gives weight lost. Nausea can indicate such disease somewhere in the digestive system. Of course, it doesnt have to be a cancer as such symptoms can be also caused by simple peptic ulcer, however you should have some diagnostics to do not miss anything. You should start with abdominal ultrasound, full blood work and upper GI endoscopy. Colonoscopy should be done as well. If no findings abdominal and chest CT should be also performed. If it is about marijuana, you should know that in some country THC is registered as a medicine which improves all cancer symptoms including pain, nausea, depression, lack of appetite and many more. Hope this will help. Regards.