My boyfriend admitted to having "a thing" for his roommate, male. How do I move forward in the relationship?

I've been with my boyfriend (20M) for three years, and we just moved in with him and our other two friends/roommates this summer. So far, despite the initial adjustment, things have been going great. Or so I thought.<br><br>I (20F) recently discovered that my boyfriend admitted to having "a thing" for one of our male roommates, before we even got together. I'm not sure if this was a sexual interest or romantic one, but I'm extremely hurt and unsure of what to do.<br><br>This came to my attention after I was joking with these two about boyfriends and girlfriends. The roommate made a comment about them already being boyfriends, and I laughed, thinking he meant us. The boyfriend corrected me and said no, that it wasn't us. That made me curious, and when we were alone, I asked about it.<br><br>He immediately became defensive, saying that it was in the past and that he "wouldn't mind" the roommate being his boyfriend. I then asked if this was a sexual or romantic attraction, and he said both. I told him I wasn't comfortable with this, and he eventually said that I could tell him if I wanted him to stop "being friends" with the roommate.<br><br>Honestly, I am extremely hurt and I don't know what to do. I've never felt like this before in a relationship. I would appreciate any advice or personal anecdotes.