If you plan on staying with him, open relationship or otherwise, I suggest you tell him. I kept my exposure from my long-time girlfriend for about 10 years and one day I screwed up and sent her a Reddit link from my "naughty" account and from there she discovered my online exhibitionism. She had always known that I was an exhibitionist and was accepting of it, but did not know that I'd been posting my nude and sexually explicit pics and videos all over the place. She was very upset that I had kept that aspect of my life hidden from her and felt like it was a betrayal of her trust. We've worked things out and have a set of ground rules for me to follow with my exposure. While she was upset initially that I was exposing myself like that, she was more upset because she felt like I was lying to her all those years, and even now she seems a bit insecure at times that I'm hiding other things from her. Based on my experience, it's probably best to tell your boyfriend about your exposure. He might not understand, but better to get it out in the open and not have to conceal it from him.