Idk what to tell him

My long term bf and I, share a vehicle and live together. I’m a f(26) and he is m(40.) About a year ago we went through a really hard time and I did meet up with a guy closer to my age in the middle of the night and he found about it. We worked through that.

Last night, I took the car out in the middle of the night. I’d rather not say what for. But it wasn’t to meet a guy. And I’m ashamed. He knows because the way the seat was left and the amount of gas missing that I left. And he’s been texting me about it while I’ve been asleep. Can anyone give me something that I can tell him rather than the truth? I’m freaking out. Please help. We’re also super broke, so he said he knows I didn’t leave to get food or anything.