Sounds like two different problems:
First, when the urethra is not blocked, you can't hold the bladder like you used to, and
Second, sometimes the urethra gets blocked and that's when you can't pee.
My wife (who is cis-) has told me repeatedly that she's amazed at how long I can go without peeing...she says that after SRS the urethra is much shorter than in a male, and its much more difficult to hold the pee. (Also, because its much shorter there is an increased chance of a UTI.)
RE: the second symptom...could it be that the urethra gets blocked due to being misrouted somehow? How long ago was SRS?