I Broke My Boyfriend's Trust With An Imaginary Partner

So, I've been with my boyfriend for a year now. We're both in grad school and we're pretty solid, same page on everything, like how long we want to wait before moving in together or getting married. But there’s this kink I’ve had since college that I never really explored because of my relationship status and the rules we set up. It's all consensual roleplay stuff with an imaginary partner, I know it sounds odd, but it's just a way for me to get out some other fantasies without breaking any promises or hurting anyone. Lately, though, I’ve been feeling a bit stifled. I told my boyfriend that I wouldn’t do anything real-world or involve anyone outside of our relationship. But there was this moment where I broke the rule because it felt so good to push against those boundaries even if just in thought and word. It’s like with my imaginary partner, but acting as if we’re together right now. So one day, while he was out, I used an app to chat with someone pretending they were my imaginary partner, just typing messages back and forth. I know it's a gray area and I felt guilty immediately after because he trusts me so much that it would be easy for him to read into something more than it is. But when we talked about it, I was defiant, I said it’s just roleplay in my head, and there’s no real connection beyond the message texts. He’s okay with it as long as it stays imaginary and doesn’t interfere with our relationship. But now every time he leaves for class or work, I’m worried I might do it again. I’m not sorry that I did what I wanted to explore once, I know my limits better than anyone else does, and I’ve been honest about how I felt during the chat. It's just this weird place where I'm straddling wanting to keep everything open while respecting our relationship boundaries, and pushing them just enough for me to feel free.