I didn't sleep well is commonly used. It would be nice to use it instead of was were
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
witty witty 764 I didn't sleep well yesterday
a completed action, a simple statement of fact.
witty witty 764I wasn't sleeping well yesterday
an ongoing activity, usually followed by an explanation or an occurrence that justified it. “I realized that there was smoke in the room!”