Bowel issues. Low fiber intake or else?

In morning as per biological cycle when i defecate i experience stool retention inside the external sphincter and it makes me feel urge to apply pressure to remove that but still some remains. There is no hard stool even the stools are not solid and it has mucous also which i think is normal. Due to retention i need to evacuate manually with finger. My diet is low on fiber but since all these issues i am taking a full plate of fiber since 3 days. But I can't have much of fiber as i have gas issues. Also the stool moves out with great force of gas in the starting. Even in whole day gas escapes out means there is no such problem of non passage of gas from anus as well as mouth. Is it the problem of low fiber intake or else?