Help with making my own wine? Is it still fermenting?

So I'm making my own bag (yes, bag) of ghetto pineapple wine with Dole juice, wine yeast, and sugar in a gallon-sized Ziploc bag. For the first two or three days, CO2 built up inside the bag, which I skillfully released while being careful to not let too much in (I have heard this is the way to do things). Additionally, it was pretty clearly fermenting; as it was foaming a lot, smelling of... well, fermentation, and generally showing some action. Now, several days later, the foaming has settled down and less CO2 is filling the bag. Is this normal process?