Nausea, Vomiting, Severe weight loss, Pain between breastbone

I am 55yr old female and have suffered with nausea and vomitting for months, however, it has now become a daily occurence. I also get severe pain between the breast bone area. AFter I vomit, i feel better but my pain can last from 1/2hr to 4hrs or more. I dont have heartburn per say. Infact, i had Nissen Fundoplication surery (GERD surgery) 10yrs ago. I have lost 15 pounds in 4 months. Episodes usually happen after ater I eat or drink - and it doesnt matter what it is. Now I have light green gel come out after i go to the bathroom and bowels covered in yellow gook. Had CT scan and showed nothing. Went to ER and they sent me home. Can't go on like this. I am not living. Keep a bag with me wherever I go because I never know when I will vomit. What can it be? Please help me.