Silence/space being added to my exported tracks!

Okay, so I’m a long time user of Audacity and have used in to both record and mix my bands first professional album at home before being sent to someone to be mastered. I recently received the final mastered tracks, but just needed to trim the tracks so that they flow seamlessly into one another. This involved my importing all the tracks to one project in zooming in on the very beginning of each track, highlighting the blank noise (space that was not supposed to be there, causing a split second pause between each song… super annoying) and simply cutting that unnecessary noise out. All of that worked fine and after playing back each start/end to the tracks they flowed perfectly into one another and you couldn’t tell where one stopped or ended. However after “Export Audio Selection” to each individual track and playing them back on say Windows Media Player I realized there was a skip added. The blank noise had been added back. I even burned the audio to a disk and sure enough, a split second skip. I then went and imported the tracks that had the start/endings edited back into audacity and zoomed in on the beginning and discovered there was space before the audio started that I cannot get rid of!
Is there a preference or something I am missing to eliminate this issue? Or do I need to maybe do this on a different program? Ive spent close to 2k on the music and I would hate for it to be less than perfect in my eyes. Can anyone help me out?? Thanks you!!

MP3 doesn’t support precise song timing. Are you using MP3 by any chance?