My boyfriend doesn’t trust me

My boyfriend and I have have been doing really well in our relationship lately. We had some slip ups in the past and we have been trying our best to heal from it. The other night he asked for space because he started to think about this one time when I called his little (he’s in a frat) hot to a friend of mine when I was trying to set them up for a date night event. The following week i was talking to a mutual friend at a party when his little got brought up because they had been hooking up. I asked her how it was in bed and I know that might sound bad but that’s how the group of girls were talking. We’ve always talked that way and I didn’t mean to cause any harm. My boyfriend took both these things and thought it was very suspicious. But I have never stepped outside of our relationship before. He asked why I did that and I told him I asked because that’s how girls in our greek system talk to each other. Which is true that is how we talk since we’re all friends. He doesn’t believe me and feels that there is more to the story. I don’t know what to tell him anymore or what to do. I have never cheated or talked to anyone else and he’s always had insecurity problems since day 1. The situation he’s having problems about took place 6-7 months ago. It’s taking a big toll on me because now im doubting my character and I dont know what else to tell him.