A Secret I'm Afraid To Tell My Partner

I've been in a stable relationship for years. We have our ups and downs like any couple, but overall, we're very happy. Lately though, something's changed. A friend introduced me to BDSM and the feeling of power when it comes to role-playing as a submissive is exhilarating. It's only happened twice and both times with someone I met online, kept anonymous. I feel so guilty and scared that this side of me will ruin everything we've built together.