Dull lower abdominal pain when standing??

Hello!

Male 17 yr old 6”3

Symptoms;

abdominal DULL pain in lower abdomen (middle)

bloating and gas 

this is is the weirdest part,

THE PAIN GOES AWAY WHEN LYING DOWN!

i could be in crazy pain from standing for too long and then as soon as I lye down the pain slowly subsided as if pressure is being released.

any ideas on what this could be?

I’ve had 3 CT scans with all clear

2 blood tests for:

Celiac, white blood cell count, inflammation (all clear)

I have absolutely no idea what this could be?? Any ideas?

 

Maybe havean abdominal ultrasound.