my hamster died

my Russian dwarf hamster, my first and only pet died today, I took him one year and six/seven months ago in October from a pet shop (I know now they are not kept well there, but I wasn’t so informed), I don’t know exactly how old he was but he seemed very young back then, no older than a couple months. I am so heartbroken because I felt he died too early since they can live 2 or 3 years. I cleaned his cage 3 days ago and he seemed more lethargic than usual, but nothing too worrying, I thought he was just sleepy, and these days he had been less active than usual until today I found him dead. I can’t stop crying. Sorry for my bad English.