This might be because of post operative oedema or if you are having some pain then it might be because of spasm of the sphincter while defecation
Both of these might lead to incomplete emptying of the bowel and thus leading to a feeling of incomplete evacuation
This leads to repeated feeling of defecation
Next Steps
consider consuming high fibre diet
sitz bath
if you are having pain then local application of lignocaine gelly before defecation
for spasm diltiazem oint for local application before defecation
hope you find this helpful
Health Tips
if still not relieved consider an appointment with your operating surgeon for physical examination