This is NOT a new pain. Patient with lactose intolerance have it for long time. It is often that they don't recognize how severe it is.
The high mark of symptom is the temporal, casual relationship between ingestion of lactose containing food, such as milk, butter, cheese in it, to the rapid (within ~10 -15 minutes) onset of abdominal pain, belching, nausea, vomiting, bloating, gas, diarrhea until the whole intake of lactose passes through the digestive tract with evacuation. This pattern repeats itself every time dairy product is consumed.
On the other hand, when there is no intake of milk based product, there is no pain.
Try home cooked meal from raw ingredient without dairy product. Bread from grocery store has milk in it. Meticulously eliminate milk and dairy from diet. If the symptom improves then there is good likelihood this is lactose intolerance.
Seek medical attention if symptoms do not improve.
Disclaimer: This site and its entire content are for informational purpose only. It is not for diagnosis and management of diseases. It is not a substitute for a medical professional. Nothing is. Seek immediate medical assistance if you feel any pain or weakness or numbness.