It sounds like you have rectal prolapse which is a medical condition where the walls of the rectum collapse or detatch and protrude through the anus and therefore become visible. You need to be examined by the doctor right away. You can start with your general practitioner but you will need to see a gastrointestinal specialist is well.
This condition occurs from frequent constipation and straining, long term diarrhea, pregnancy and stresses from childbirth.
Rectal prolapse progresses over time and doesn't get better by itself. If you suffer from constipation then you need some stool softeners to make defecation easier. Sometimes surgery is necessary. You do need to be evaluated by a specialist as I mentioned earlier.
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Rectal prolapse can cause lower back pain. As far as feeling weak and tired alot, I recommend that you make an appointment with your doctor to have a physical exam and blood work done. If you are anemic then you would feel tired alot and would need iron supplements. This would be determined from your blood tests.