If you called me to describe the sudden onset of this, I would advise you to go to the emergency room immediately.
This question includes symptoms of abdominal pain and weakness (which the person feels and describes) and a sign, low blood pressure, or hypotension (which is detected or observed). (Here, I am assuming that the person asking the question has a way to check and detect blood pressure and knows that it is low, such as with a home blood pressure cuff.)
The answers to this question depend upon whether the symptoms (abdominal pain and weakness) and the sign (low blood pressure) are acute or chronic. They could be serious and life-threatening with either, but if they are acute, then it would be important to seek immediate medical attention.
If these symptoms and sign are chronic, the problem could be serious, and there are several possible diagnoses that require consideration by a doctor. One possible cause is rare, which is why I am mentioning it here, because it can be easily missed: adrenal insufficiency (Addison's disease). President Kennedy had this disease, in which the adrenal glands stop producing substances (cortisol and aldosterone) that are vitally important.