Without sufficient water and oils in your diet, eating more fiber can actually increase your constipation, can definitely result in bloating and can definitely result in cramping and pain. It was a vicious cycle I rode for far too long.
Short term for the pain, drink warm (fresh) ginger tea, warm lemon water, or plain warm water (all of these without sugar). After it has settled in for a while, lay on the floor with your legs on a chair (90 degrees at your hips and 90 degrees at your knees). Breath slowly, with very gentle massaging of your abdomin. This should help to calm the cramps and help to release some of the bloat causing gas.
When I get badly constipated I am careful to not pack more food on (small, warm, moist meals), but increase the water and oils for a couple days (sesame, olive, flaxseed oils are very good). You could begin experiencing relief within a day, but likely it will be a couple before you really feel the benefits.
Watch the fiber. Flax oil is a good source of gentle fiber, plus the oil minimizes the drying affect fiber can sometimes have. Otherwise oat bran, psylium powder, and similar fibers can be improved by sauteeing them in oil before eating them in a meal (I do 2 parts oil to 1 part fiber). This minimizes the potential for cramping that can come with eating fiber, which is partly due to its coarseness, partly due to the gas created by the bacteria that are having difficulty digesting it.
Make sure you are getting plenty of water with any fiber you take. If you put a teaspoon of psylium powder into an 8oz glass of water it will thicken to the point of not flowing. Imagine what happens when insufficient water is provided. You can almost make concrete with it. Drink plenty of water, room temperature at the the most, but warm is even better. Cold water will interfere with digestion, and that is not desirable when your constipated.
Long term; learning what and how to prepare food that works best for you could minimize your challenges and possibly help you avoid losing any part of your digestive organs.
I have had some good results from what I have learned over the past couple of years (after a couple of decades of experiencing, what you have described, too many times to remember). I am happy to provide more info if you would like, just ask.
And, certainly, be in contact with your doctor to avoid any potential serious consequences from your current situation
Constipation triggers for me include, dairy (esp. cheese), beef, minerals (calcium, iron), too much dry food (crackers, bread,) bananas
Cramping and bloating triggers include, tart or astringent foods (cranberry, pomegrante juice), tomato skins and seeds, strawberry seeds, grape skins, dry fiber (granola bars)
Hope you find relief soon!