What Causes Severe Stomach Pain And Vomiting?

Hi.. on monday I woke up wih a really bad stomach pain.. then started feeling sick and vomited four times in the morning.. then felt a bit better but the pain was still there.. ate a bit a lunch.. then around four o clock had toast and butter after ten minutes the pain got worse and couldnt move. Had couple of paracetemol and went to sleep then felt better had dinner at night.then at midnight around two the pain got worse for around fifteen minutes and then it went mild.. woke up in the morning and again the pain started but it wasnt as bad as monday but still had mild pain on the left side stomach all day.. on wednesday the pain was gone but had mild pain on my back.. sometimes feel better when I burp or fart. My stomach been rumbling a lot in the couple of last week.