Many people suffer from occasional low back pain and constipation. You need to drink more water and get off the carbonated colas whether they are diet or regular. Get off the fruit juices because like the regular sodas they are full of sugar and as a type 2 diabetic, you do not need that. Avoid high calorie, low nutrition snack foods such as pretzels, potato chips, candy bars, and even most protein bars because of the hydrogenated or partially hydrogenated oils and trans fats.
One of the fastest ways to tone up your digestive track is to get in the habit of drinking a couple of 16 oz glasses of fresh green smoothies made at home. Most over the counter pre-packaged green smoothies are loaded with sugar and other things your body doesn't need. You should be making green smoothies with fresh celery, kale, baby spinach, cucumbers, apples, red seedless grapes, avocados, navel oranges etc. I personally use a Vita Mixer and would not trade it for any other machine on the market. That is not to say there are not other machines that are very efficient. I also prefer a Vita Mixer as opposed to a juicer as I get all the fiber and nutrients in the drink instead of throwing they away.
Here is a link you might like to look at: