I Started With Hard Pain In Upper Stomach Before Eating

I started with hard pain in upper stomach before eating and since then (yesterday evening) I have been throwing up everything I eat within 20 minutes of eating it. Also vomiting bile (yellow-greenish liquid). Constant nausea when stand or sit; dealt with best by laying reclined in bed. Stomach pain has largely cleared up but continue to have pain/discomfort at bottom of sternum. Nibbled slowly at 4 crackers an hour ago and so far has stayed down. Taking anti-nausea and antacid medicine. Any ideas?