could he be looking through my texts?

my boyfriend and i got into an argument about something so small and stupid. anyway, he brought up some of the things ive said to my friends in my texts. they were harmless but weren't exactly okay to say either. he is NOT the type to go through my things at all but we did break up for like a week a couple weeks back. could he have been checking to see what ive done while i was single? it really shocked me on how he knew this information.