Given your description of abdominal pains and morning discomfort, it seems that it could be connected with an irritable bowel syndrome (IBS) due to your previously diagnosed lactose intolerance, as one of the possible causes (among the others, such as emotional stress, stomach and bowel inflammation, fructose intolerance, etc.). Your family doctor might refer you to a gastroenterologist, who could control and follow up your specific and personally tailored lactose restricted/reduced dietary regimen, combined with proper digestive enzyme supplements as well as supplemental calcium and vitamin D. You might also want to try controlling these symptoms with OTC antiacids (but this way is only symptomatic, not taking into consideration the actual underlying cause, which is not as valuable as an evidence based medicine causative approach).

Given the data about the heartburn and acid reflux, your doctor might also want to check (via laboratory blood or stool tests) the possibility for Helicobacter pylori gastroenteritis, easily treated with triple therapy (as another possible cause of your symptoms).