Problema na rede neural

Estou tentando fazer uma rede neural de multi-classificação, o problema é que na hora de calcular a loss ocorre o seguinte erro

utilizo o otimizador: SGD

utilizo o calculador da loss: BCEWithLogitsLoss

--------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-62-2b30ec84cb8b> in <module>()
     15 
     16 
---> 17   loss = criterion(pred,rotulo)
     18   epoch_loss.append(loss.cpu().data)
     19 

2 frames
/usr/local/lib/python3.6/dist-packages/torch/nn/functional.py in binary_cross_entropy_with_logits(input, target, weight, size_average, reduce, reduction, pos_weight)
   2431 
   2432     if not (target.size() == input.size()):
-> 2433         raise ValueError("Target size ({}) must be the same as input size ({})".format(target.size(), input.size()))
   2434 
   2435     return torch.binary_cross_entropy_with_logits(input, target, weight, pos_weight, reduction_enum)

ValueError: Target size (torch.Size([20, 1])) must be the same as input size (torch.Size([20, 6]))