Diarrhea in the middle of the night & chewing
I have a Bernese Mountain Dog puppy. She's 10 months old. We were doing okay, but now, she's pooping at about 3:00 am. She does it near the door. Sometimes, she wakes me up, but the last two nights, I've come down to an unpleasant mess.
In addition, she's chewing on the throw rugs around the house.
It sounds as though your pup has done very well up until now. Any sudden change in behavior is cause for, if not concern, then evaluation at least.
I'd recommend making her last feed of the day a bit earlier than you are right now, and then ensure that she has a potty break right before bed. This should mean that she doesn't actually NEED to eliminate at 3am. It's likely though that this has become a habit rather than a necessity. Although if she's having diarrhea then it's possible she has an infection of some sort (bacterial or parasitic) that needs to be addressed.
I'd recommend having your vet check her over to rule out any underlying health issues. If she gets the 'all clear', then using a crate to contain her at night would be my suggestions. She's unlikely to mess in it, especially as she is pretty much housetrained and 10 months old. Check out my Crate Training page to learn about crate training.
The sudden chewing on rugs could be a sign of stress, as she's past the teething stage and this is a new behavior. Dogs chew as a way or relieving stress, boredom, anxiety and so on.
Is it possible that there's been some kind of change or upheaval within your household that has triggered these behaviors. Maybe a change in routine, a new house, a new baby, a vacation, underlying stresses that are affecting the family members and so on. Dogs are very sensitive and pick up emotions from their owners, and because they don't understand the root cause of the emotion they tend to react anxiously.
If this is the problem your pup will likely settle down soon as she adjusts to the new situation, and this behavior should disappear.
Hope this helps, best of luck with your puppy.