I’m sorry Chloe, but there are a magnitude of weird things here. Your loss function should be separate from your model. It most often only consist of a function (not using nn.Parameter - thats the model) and returns a scalar.
Dont do zero_grad before your backward and step. Do the zero grad before sending inputs to the model (in your case model = LOSS(x))
Perhaps start with a tutorial/prebuilt project to get the basics down and modify a single part of it   Even brushing up on your Python seems like it would help