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It is not possible for the female genitals to store semen as the sperms die off after 5 days by themselves.The odour can be due to hormonal changes in the body as after Hysterectomy there is a sudden drop in the female hormones so that might be a possibility.
Even infections as yeast,bacterial vaginosis can present like this.A pelvic examination and Pap smear would help in ruling out the cause.Kindly visit a Gynaecologist for evaluation.
Take care!