Testosterone went from 538 to 289 in 7 months. 19 y/o Male.

19 years old, Caucasian, White

Sup everyone, I did blood work for Test out of curiosity, one in Feb and one Today. My testosterone severely dropped and I am very worried. I’m 19 years old, I’m perfectly in Shape (I’m on the skinny fat end, 20% BF), and I eat a perfectly normal diet. I eat meat and everything. Probably 2000 cals a day, 110 g of protein (I weight 140 lbs) Generally, I don’t feel very motivated. I honestly have pretty low libido. But I never expected my Test to drop such an extreme amount. What could this be?? I Ty ought even 538 was on the lower end , but 289!!! That’s insane. Can someone please let me know their thoughts?