All the major plumbing codes require supply and waste pipes to be firmly supported and they specify the types of connectors to be used and their spacings. There is no such thing as a too firm connection (short of actually damaging the pipe or the supporting structure). The only exception is in pipes that must pass through perimeter foundation walls. These are passed through openings that allow for some differential movement, especially foundation settlement.
It sounds as if you may have poorly supported supply pipes in your walls and ceilings. Another possibility is that the timbers supporting your bathroom are inadequate and flexing under weight during use.
NtP
