Answer:
I think, you were sleeping like a dog
Step-by-step explanation:
A past perfect continuous tense is when an action started in the past and continued up until another time in the past. So it's still in the past but it was happening for a time in the past if that makes sense.
Changing sleep to sleeping makes it sound like it was happening for a period of time, instead of just sleep.
I added were instead of are or other words because again it started in the past and led up to something in the past, so it isn't occurring at the moment.
I hope this makes sense and I could help you!