Constipation. Be highly appreciated.

Medical history: Constipation for last 10 yrs., have piles and also had anal fistula. I got operated for anal fistula last year in May and its gone. Piles is still there. Also, I have problem of gas for past 3-4 years. I have constipation for more than 10 years. I have improved my dietary habit but still, stool does not pass easily. I have observed that the my stool is not sticky (90% times) and is normal stool. I have also observed that that the stool has some hard stool stick to main stool here and there. These hard stool manly found on the front of the stool but can be found till 6-7cm down the length of stool. I have gas problem as well. It has been there for last 3-4 years, but it is getting worse. I believe my large intestine itself has some problem. But I am not sure. Any help/advise will be highly appreciated.