I'm certain this is the case with me, too. We had cats with fleas growing up and though i didn't get officially sick until 25, there was always something different about me. Poor memory, frequently sick, terrible hangovers, slow to recover from workouts etc. Looking back, this has always been brewing
This is so close to my own story. I think I got bartonella and lyme when I was very young. I had low-level symptoms for years, a mix of stuff like concentration issues, vicious hangovers, anxiety, insomnia, fatigue. It would always wax/wane in cycles too. I had a feeling of impending doom. Lo and behold at 24 is when I fell truly sick (maybe I caught a flu that helped trigger the underlying infections), and I became bedridden and all the previous symptoms amplified 100 fold.
As to the original question, it's hard to know for certain when you may have been infected. But yes, it's highly possible it originated in your youth, possibly from the fleas.