Confusion over purchased albums and songs on Apple Music and iTunes

I've purchased albums through iTunes and Apple Music. Now I'm not sure if I am getting credit for my previous purchases. For instance, I purchased 3 Jesse Cook albums years ago, the whole album. If I go to the Account heading at the top of the Music app and select Purchases, the page that comes up tells me about my purchases. If I select the All button and the Album button, the page tells me that I have purchased 3 albums. If I select the Songs button, it tells me that I have only purchased 7 songs. There are far more than 7 songs on the 3 albums. If I go back to the Home page for Apple Music, and select Jesse Cook, I can select one of those purchased albums. If I go to the ... symbol to the right of the page, and select show in iTunes Store, the next page tells me that I have purchased all of the songs on the album. I can do the same thing with one of the other Jesse Cook albums that I previously purchased. However, if I select the 3rd album, and repeat the process, it gives me the option to purchase the album, even though I have purchased it years ago. What is going on here? Have I wasted a good portion of the money that I spent years ago? Am I not going to get credit for all of those previous purchases?