Hello and welcome to H.C.M. forum . The sciatic pain is mostly caused by vertebral disc herniation , spinal stenosis , degenerative disc disease and rarely piriformis syndrome . In your case the general lack of muscle strength and ageing can be the most probable cause of both Sciatica and Rectocele and Vaginal prolapse . There is no evidence that getting pelvic prolapse will cause sciatica . I would suggest you to go for improving your general health through a regular exercise regimen (preferably guided by a physiotherapist ) and also a balanced diet .