When should i get results back?

I have stomach pain since sunday right in the middle just bellow the rib cage of my stomach. The pain wakes me up in the middle of the night and it hurts of and on through out the day, and in between my shoulder blades hurt. I went to the doctor for it Tuesday because it hurt so bad and the doctor told me a couple things it could acid reflux, ulcer, or gallbladder. He took blood and set me up with an ultra sound for next Friday. He also gave me a prescription for ulcers and acid reflux. Wednesday the doctor called me back and told me that he was putting me on a amoxicilin because my blood test came back that i had some kind of infection and the had to do further test with blood and they would call me back. Well i have not heard from them yet and i was just wondering what the further test would be for. Anyone know?