Chris, how hard or easy was the catheter insertion. The last time i went into sudden and full retention they had to stretch the bladder neck to get the catheter in and that was the day after a very minor and gentle dilatation.
My slowly developing retention was preceded by a slowing flow as the scar tissue swelled up to block the urethra The first retention was a surgical clip in the bladder.
Any blood in the urine , could be bits of scab blocking the bladder.
The retention when walking sounds like something could be settling in the bottom of the bladder.
Thanks Chris