The hormone treatment causes aches and pains in two main ways:-
1. Fatigue can manifest as aching muscles and limbs that feel too heavy to lift
2. Your body is feminising - ligaments slacken off and the pelvis starts to widen out, muscles lose tone which means that what you would consider to be normal activity becomes harder work and you can ache more afterwards.
PCUK ran a project on HT induced fatigue a couple of years ago, it is worth giving the nurses a call. Also, if you are struggling to exercise, swimming is known to be very good for men on HT as it is low impact. We just need all the pools to reopen :-/