Hi, that s sounds serious. You are suffering from a condition called Malena (black coloured stools ). I t happens when you have gastric ulcers from where small blood keeps on oozing , which gets digested with food and stool becomes black Naturally you will feel weak and weight loss. You have a tendency to vomiting too, after food, which points to your GIT pathology. You need to be thoroughly investigated and treated,. My advice is to get admitted earliest to a hospital where investigations and treatment can be carried out. Hope this helps.