RT side-effects are cumulative. I had RT over a six and a half week period (32 sessions). No real side-effects for the first month. For the final two weeks and several weeks after treatment a need to pee frequently, due to the radiation irritating the bladder (a very common side-effect), and I started passing a lot of clear mucus from the rear end - again very common.
Bladder issues cleared up within a month of the end of RT. Bowels took longer; pretty much back to normal after 6 months, and now (two and a half years after treatment) just a very, very occasional mucus "mishap".
Cheers,
Chris