Truffles chocolate trouble..??

ok here it goes ive been trying to make these very nice sweet great tasting chocolate truffles that you take a melon baller and scoop out into little well ever time i try to make it it doesnt go hard enought for me to dot hat and when i do sort of try to get it into whent hey get into the freezer then flatten down they were made with milk chocolate coco condentenced milk vanilla and cooked till it was think shinny and creamy and it tastes great but it wont hold shape what can i do or what did i do ever recipe i get tell me to do the same thing what could i be doing wrong