I have been spottong every two weeks after my period for the last 4 months. i do have cysts but don't know why im spotting?

Not always cysts: Depends on whether you are on birth control or not. It is common to have "breakthrough bleeding" on some birth control pills. Simply taking a "stronger" pill often is all one needs. Cysts are common and most people don't have cyclic regular spotting despite having cysts. Without doing an ultrasound i would not assume that cysts are present or are anything more than an incidental finding.