Lost many of my downloaded CDs on my iPhone

Hi there, I have a very complicated question and problem. I had an iPhone 7 and recently purchased a new iPhone 15. On the transfer of my iPhone 7 to the 15, a good many of my songs didn't transfer. I tried syncing my iPhone 7 with my computer (a MacBook) to try and get the rest of the songs but this didn't work. I then (now I know stupidly) tried to purchase Apple Music. When I did that, many of my songs said "Waiting" on the sync on the computer and I ended losing most of them. So I immediately cancelled Apple Music, hoping that everything would go back to how it was. However, when I looked on my iPhone 7, I saw that half of my music collection was gone- about 1,500 songs- most of them are CDs I downloaded years ago. Is there any hope for restoring these? I am furious that Apple has cost me $1500+ worth of music.