Hello,
are your input (images?) rescaled between 0 and 1 ?
I saw that your model output is 1. Do you mean to use sigmoid activation ? if so, then it is not included in BCELoss.
If that is the problem, some parts of this discussion may help:

  
    
    
    BCELoss vs BCEWithLogitsLoss 
  
  
    What is the advantage of using binary_cross_entropy_with_logits (aka BCE with sigmoid) over the regular binary_cross_entropy? I have a multi-binary classification problem and I’m trying to decide which one to choose.