The pain produced by water (I assume cold) is not unusual for a newly replaced filling. However, the spontaneous pain that wakes you in the middle of night is not. The tooth or teeth waking you up have a very low probability of getting better without treatment.
The reason we do not like to have endodontic (root canal) treatments performed, is that it usually relies on toxic materials to seal off the space where your nerve used to reside. in addition, the tooth now is only partially "alive" and often, an area of less vital tissue around the tooth is found. There are people who tolerate root canals better than others.