As per your letter,Pain is in the left side of your abdomen.But,Ultrasound
revealed fatty liver
.Liver will be on the right side below rib cage.So,pain due to fatty liver is excluded.
One possibility is Left Renal/Ureteric stone which might have been missed in Ultrasound.
Please consult your doctor and ask for an IVP(Intra Venous Pyelogram
) which detects any obstruction in the Urinary tract
If it is normal too,then it may be musculo skeletal pain.If it is not relieved by Muscle relaxants,you have to get further investigated with CT scan abdomen.
Wish you good health