Puppy blues... Has anyone ever experienced this before?

Hello everyone!

So we just got a puppy and it's only been 10 days now. She's adorable but very stubborn. She cries, pees and poops everywhere and doesn't like being put on leash for walks. We just started puppy training but she isn't every receptive.

She's a cavalier king charles spaniel puppy of 11 weeks. I thought this breed was usually calm and easy to train but we have hardly slept for the past few weeks and it's making me regret getting her :( am I a bad mum? How did you deal with puppy blues?

It's something people hardly ever talk about and I feel bad for feeling this way...