I'm beginning to hate my iTunes experience!

When I first got iTunes, I loved it. I enjoyed hearing whatever I wanted. Over recent years, however, I've noticed more and more that any song or album that I didn't buy through iTunes has "grayed-out" if you will, and can't be played. It is getting increasingly annoying. I don't know how to fix it. Once I downloaded the albums that I had gotten over the years on my own, I threw them out...thinking, "I don't need these anymore!" Now, I've lost many, many songs. Any suggestions? And, just FYI...I'm old.