Every time my stool is thick, i feel that my anal fissure tears again. it hurts for a few days then goes away after the defecation is smoother. is surgery needed?

No: If u get better with diet modification, no surgery is needed. Add some fiber and it will help as well. U should b getting close to 30g of fiber per day.

Try stool softeners: First and get a regular bowel habit with loose stools. Surgery is last resort. Use plenty of fiber and water to keep stools soft. Add colace (docusate sodium) and senekot if needed. If keeping the stools soft does not let the fisure heal and stay healed then surgery may be needed.

Surgery is good: This condition responds extremely well to surgery, which isn't nearly as bad as you might think. If you've been suffering for more than three months, quit putting it off and see a general or colorectal surgeon.