First, make sure you have not set Automated Gain Control in Render / Player Options / DSP in the Export dialog.
Second, if you are exporting to WAV or AU and using floating point (or to MP3/Vorbis/Opus), and you are playing back on a Windows system, then Windows will apply a limiter during playback if your audio is > 0dBFs. See level meters during playback as Saga Musix mentioned.