If you have been experiencing stomach pain, bloating, and constipation for the past 3 days, it is recommended to try taking a medication like PEG-3350, which is a powder that can be mixed with liquid and taken once a day as needed. This is often the first line of treatment for constipation. If symptoms persist or worsen after trying this medication for 5-7 days, it is advisable to consult a healthcare professional for further evaluation and treatment.