On the surface, your symptoms sound like
appendicitis. Your elevated temp, the referred
pain, all points to that.
Sometimes ultrasounds do not reveal the true issue - they are not detailed enough.
Personally, I experienced appendicitis much like you are experiencing. The "twist" was I had a cyst in my intestine as well.
It took surgery to locate the problem(s). No test - and I had them all - revealed the truth.
Go to the hospital. They are probably thinking you are drug-seeking.