Been feeling a pain in my back that felt like someone punched me. pain spread through to my stomach and felt like vomiting. what could cause this?

See your doctor: Pain in the abdomen can be caused by many things. While there is no way to say for sure without a more detailed evaluation, pain in the abdomen that starts in the back can be from gall stones, the pancreas, kidneys, or the aorta to name a few. I recommend seeing a doctor. Your doctor will need much more detailed information and a physicial exam to give you an answer.