I have breakthrough bleeding on birth control pill tri sprintec?

Possible effect. Breakthru bleeing may occur in low dose BCP, not so much in the full dose BCP. Happens at times in normal too. If rrecurs, gynecologist and check for polyps in endometrium. May have ultrasound of pelvis.
Breakthrough bleed. can occur on the pill,also if you miss pills,or have an infection. Make sure you take the pill the same time of day (within 1-2 hours). If it continues see your doctor.