If you think you have a lack of stomach acid there are simple tests that can be done. I have been taking hydrochloric acid capsule for almost a year now and they have definitely helped with my digestion. However they were still not enough, so now I am on a 2-phase tablet that releases hydrochloric acid in my stomach and pancreatic enzymes in my instestines. It has further improved my digestion. But my experience is that neither will improve your constipation if other factors are not addressed.
Get a copy of "The Auyervedic Cookbook" by Amredea Morningstar. Not necessarily for the recipes, but for information that will have you looking at food and your body in a very different way. A way that has helped me conquer my IBS and is aiding in my elimination of my constipation. I have the added benefit of having found a great naturopath that has training in Auyervedic medicine, so I may not have had the same result by just reading the book, but it was a very helpful starting point.
I know there is a lot of "junk" out there on natural and conventional healing, you just have to explore and find what works for you. Auyervedic has done right by me, so I pass it on for anyone willing to consider it.