The fact that it is not constant is a good sign. Could be a partial obstruction working itself through, or something as simple as indigestion and gas. If it is not severe and you do not have other symptoms, such as fever or shortness of breath, you can wait and see how it goes. Even if it is a partial obstruction, you can wait and see if it resolves on its own or gets worse. I've had them take a week to resolve.
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