Why has my manually uploaded songs on Apple Music disappeared?

I have recently become aware that music I uploaded manually years ago (like from actual CDs) is no longer appearing in my Apple Music account. I don't know how long this has been the case, because I hadn't gone looking for it before, but I'm very concerned now as there was music that I can't get back and is not available anywhere else. Any idea what might have happened? This music was in my iTunes app when it was iTunes. Now with the digital takeover of Apple Music I can't even tell what I have in my Apple Music app from manual uploads vs what has been saved from Apple Music. Was this a widespread change with Apple Music? Is there anywhere else on my computer where I might be able to find these older music files? I searched and nothing is coming up.

[Re-Titled by Moderator]