I am a 47 year old female with diabetes type 2. I have recurring constipation frequently and have to take me?

I have to take metamucil daily. It becomes severe with abdominal pain and nausea at times. As a young child I was allergic to milk and thought I'd outgrown it but my dr. wants me to stop all dairy products for 2 weeks to see if I am lactose intolerant. This has been going on for over 2 years. Do you have any ideas?