Prolonged Constipation. Normal again.

I have been suffering from constipation for a year. I consulted several doctors and went through diff treatments. I went through sigmoidoscopy and the result was positive, the doctor mentioned there is no problem . Prescribed medicine like Prueease, husk powders like Pegfibre and had put me on a diet, I followed the diet and have been  following it. But there is no improvement. After some months I had visited another doctor, he performed anorectal manometry and the results were positive this time as well. He prescribed some laxatives and medicines like Lubowel 24mg. I used it, I see no major change. I have changed my diet , I used medications but nothing seems to work. Surprisingly, ducloflex tablet , which is just around 10 rs a sheet, when I took 1 tablet before bed, gave me a better experience than any other powders, laxatives and medicines. I felt like everything came out and i felt relieved whenever I used it. How to treat it, I desperately want to feel normal again .