Why do I have constipation and lower abdominal pain for more than seven years?

Hello doctor,

I am a 24-year-old male with 138 lbs (63 kg) weight and 6'1 ft (185 cm) height. I have had gut problems for over seven years. I usually have constipation and feel like my intestines are wrinkled, unable to let anything pass. The area around my groin (lower part, not my stomach) stays bloated, tender, and painful nearly all the time. Even if I manage to empty my bowels, it does not relieve the pain. Sometimes, I can be painless even after not emptying my bowels for three days or more, so it does not seem to correlate with the amount of "material" the intestines carry.

I cleaned up my eating habits six months ago, but it did not help, so I visited my general practitioner. I had a colonoscopy and blood work done, and it did not show any intolerance. So my general practitioner says I can rule out IBD and intolerance, but I have no idea what to do now. I tried to link it to psychosomatic reasons. Still, it does not seem to correlate either because I usually get a worse mood after experiencing this discomfort. There are some safe foods I know that do not cause this, but it is hard to find more of them because the pain usually lasts for days, during which time it is impossible to tell whether the food I eat is safe or not. I do not know what to do or whom to visit because it is a finished thing for my general practitioner since we did not find any problem in the colonoscopy or blood work, but I am suffering all the same. Kindly help.