yes definitely consult a physician.
i am an EMT and we generally need more information to go on .
have you noticed any thing odd before your symptoms occured?
were you struck in the stomach? coffeground like vomit?
are you allergic to anything? have you come into contact with that substance?
are you on any new medications? new prescriptions? over the counter medications? taking ibuprophen for head aches?
do you have a past medical history with stomach problems? diabetic? pregnancy? heart issues? migraines?
are there any events leading up to your pain and weakness? playing sports? car accident? a fall? fighting?
go see your doctor and be prepared to answer those questions, it will help them figure out what is happening.
When I feel like that it is because I have not eaten enough and I am hungry and my blood sugar is low.
That could be, literally, thousands of things. If you're concerned, see your doctor.