Im also in training for my first tri, did a mini one in the gym yesterday.
Bike 13K, run 2.5K then swam for 18 lengths (not non stop yet)
Suprised that i feel ok today, no pain so next sunday can increase the distance.
I have only 7 weeks to go so need to improve my swimming, have a block of 6 lessons booked starting tonight to improve my technique