How to diagnose unexplained constipation which comes and goes? stool tests came back negative from parasites, other symptoms occurring now, muscular and joint pain accompanied by occasional itchiness

By working with Dr: Each person with constipation needs to be sure there is no other disease causing it. If constipation is just due to slow movement of the food and poop through the gut, then the things to try are vegetables, water, fiber with water, prune juice, prunes, polyethylene glycol, Senokot or other senna, milk of magnesia, other laxatives... A doctor can evaluate to check for anything serious.