bf is depressed

recently i’ve noticed a major decline in my boyfriend’s mood. he isn’t as silly and playful anymore and he’s always tired. i understand he works everyday but i get nervous now when i see him on the weekdays bc i know he’s gonna be grumpy and tired and just wanna sit around and do nothing. i talked to him about it and he said the only time he actually is in a good mood is when im around, he’s just tired. he said he is depressed bc of his life circumstances and it has nothing to do with me. it kills me so much to see him decline like this and i can’t do anything about it. i just wanna do whatever i can to make him happy but it’s hard when he says there’s nothing i can do bc im not the one making him depressed. i always compare how he was to when we first started dating he was always so happy and bubbly and now he isn’t as much. i really need advice.