Losing weight and unstable on feet

[Cravenkiss]

Hi guys, so my kitten, Diablo, 2 months ( his pic attached) is being really weird and in bad shape lately. His mum dissapeared not so long ago, about 2 weeks but he was just fine until recently, he lost so much weight and can't walk or stand properly, losing his balance and looking really weak. I will bring him to the vet tomorrow, but I would like to know if anyone ever had this problem before and it there's something I can do in the meantime. Any help would be really appreciated please, thank you..