My 9 week old kitten losing weight?

for the past week my kitten hasnt been well at all i had ran out of kitten food and had to jump to shop quickly and the y only had adult cat food, i hac put a little in her bowl just to give me time to get to a bigge rshop for kitten food. and ever since shes been sick alot and now she wont touch her food atr all and she has been very anti social which isnt like her at all. help me!