Left flank pain

I have been having dull pain in my left flank under the ribs and it sometimes radiates to lower back after eating (couple of weeks now). only happens after large meals like pizza or steak and lasts an hour or two. sometimes I get severe pain in my left abdomen for about a couple minutes after a big meal too. My doctor ordered blood tests and my pancreas Lipase was a bit high but nothing unusual at 74 UL. He has ordered Ultrasound and I have an appointment next week. Some people say this is not high enough of enzyme to be concerned about but then my question is what could cause this pain if it’s not pancreatitis? is my doctor doing the right thing by ordering an ultrasound? he doesn’t suspect anything else other than the pancreas and kidneys were normal in blood tests and ultrasound. thanks.

also forgot to add that i’m on disability due to extreme severe weakness, chills and fatigue and diagnosed with Myalgic Encephalomyelitis from an unknown cause for 2 years now.