Why do I have a swollen uterus only after I have my period?

Water retention. Around the menses many women will retain water. The lower abdomen will swell and bloat. Most women cannot see uterus unless they are pregnant or have an enlarged uterus . If one is able to "see" their uterus, a trip to the gynecologist may provide an answer. A pelvic exam will be done and if needed a sonogram.