I took a trip to Cuba the month before last.
Two months ago, due to the heavy rain in the city of Seattle, the city's famous onion field was entirely destroyed.
My mom paid my cellphone bill the month before last.
The previous previous month (remember that 々 just repeats the kanji before it) is the month before last.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.