Thanks for posting your query,
Dull constant pain under right rib cage
is usually due to either liver or gall bladder
I would suggest getting this evaluated by a physician for an accurate diagnosis and appropriate management.
He/she may advice you for the following :-
1. Complete Blood Count
2. Liver Function Test (LFT)
3. Serum Amylase
5. Serum Lipase
I hope this information has been both informative and helpful
You can consult me again directly through my profile http://www.healthcaremagic.com/doctors/dr-saurabh-gupta/64132
Dr Saurabh Gupta.