Nose bleeds cannot be controlled and are a much scarier and rare occurrence than the urge to pee. Everyone has to pee every day; most people do not have nose bleeds everyday. It is possible to train oneself to pee less for the urge is often spurred by habits or thoughts. Controlling those thoughts and eliminating those habits makes one less likely to pee.
People are jumping to scary and dire conclusions when the only symptoms the OP complained of were waking to pee at night and dehydration. Maybe if the OP elaborates a bit more we can narrow down the diagnosis. However, I doubt the OP just "forgot" to mention severe fatigue, sore muscles, and poor performances which are the primary symptoms of overtraining. Poor sleep is a symptom of overtraining, but it is also a complaint of millions of non-athletes. No need to scare the OP with horror stories of overtraining and mono which ruined people's lives.
I wake to pee once, sometimes twice, a night and am perfectly healthy.