how do I make my goat cheese creamy?
I'd say the buttermilk was a necessary ingredient that you shouldn't have left out. Milk usually needs to be inoculated with some kind of culture before your rennet (or lemon juice in this case) will successfully curdle it. Buttermilk is cultured (which means it has an active colony of beneficial bacteria), and would work well to inoculate your goat milk.

Leaving that out made the milk much more difficult to curdle, and left you with a less stable curd.