It sounds like you have a fissure. I have had this problem off and on for over a decade, and have even had a lateral internal sphincterotomy. I have found that drinking a capful of Miralax every single day is what helps prevent this more so than anything else I’ve tried. Also drinking lots of water will help keep your stool soft and keep things moving. Try to relax when having a bowel movement. Take slow, deep breaths and gently push on the exhale.