Food allergies all of a sudden.

After having cows milk I get stomach pain bloating and gas. This started very recently like few months back. I have been drinking milk from my childhood. Never experienced this before. Also eating cashews is giving me stomach pain. Sometimes eggs when I eat it for dinner. But when I drink milk with breakfast I'm not noticing gastric issues. But cashews trigger severe abdomen pain for hours. Why I have got these food allergies suddenly? Also the nutritional deficiencies of vitamin d and calcium are recurring. Recently was tested low on ionised calcium and vitamin d. Calcium deficiency has caused ankle pain as told by orthopedic. Even with milk allergy I am having a glass of milk with breakfast. What should i do about this. ?