Very light bleeding at normal time of period for last 3 month .ttc. hpt negative each time. is this due to cyst or due sperm quality .?

Many causes: It is good to consider pregnancy whenever your period changes. Since it is negative that is less likely (but not impossible).One's age impacts quality of periods, as do several medications. If any new meds or changes, consider that as cause. Some medical problems like thyroid and ovarian problems can impact bleeding. Cysts usually will not lessen bleeding nor does sperm have an impact.