Just finding this site is such a help. I can identify with so many of the stories. Maybe my experience will help others. I am male and 67 years old. I started seeing doctors about my bowel problems, diarrhoea and constipation, nearly 40 years ago. I have heard it all from the docs; it was stress, IBS, but finally, Coeliac disease.
I went gluten-free, and apart from the odd accidental "glutening" the problems were much eased for about 10 years. About 25 years ago, it really became chronic constipation. I started taking laxatives frequently, until it became almost daily. Also, the dose had to go up. Eventually, the various doctors prescribed the laxatives, stool softeners and micro-enemas that I need for any kind of bowel movement.
I have had all the issues that you are warned about: bowel pains, anal fissure, inguinal hernia, vomiting, bloating, lack of appetite due to being bunged up etc. About 5 years ago, I had a night-time urinary problem. Tests showed Diabetes, though only just. Then, nearly three years ago, the nurse mentioned that my blood iron was high. Further tests, including a genetic test, showed Haemochromatosis. This is where the gut absorbs too much iron.
I had been a blood donor, and the Coeliac disease reduces iron absorption, so I was diagnosed 10 or 15 years later than the average male. Of course, excess iron in the blood is a well-known cause of constipation, as is diabetes, a gluten-free diet and long-term laxative usage. The treatment is easy enough; I go along to hospital, and they take off a unit of blood, about 450mL here in the UK. I had about 13 of these to get down to an acceptable iron level in 2013, but still need about 8/year now. I'm having one later this morning. It hasn't really helped with the constipation, but should help protect my heart and liver. It's serious. My dad had all the same symptoms as I have, undiagnosed, and died from a heart attack at 66.