It sounds possible that it could be levator ani syndrome, because I had those feelings, I went through a lot of tests including a sigmoidoscopy to rule out other causes, they did find some piles which my doctor had previously said I didn’t have they can cause that feeling of something stuck in the bum , I was sent to a physiotherapist one who specialises in the pelvic floor , when they do a examination if they find tenderness in the levator muscle plus the symptoms and absence of other causes they usually can then diagnose this condition, it could be coming from the womb though have they ruled out fibroids, they can cause a pressure type feeling,
but mine was a distinct pressure in my bum and very uncomfortable to sit and almost a constant aching feeling sometimes I had bad muscle spasms that felt like a knife high up in the rectum .
