My boyfriend and I have been together for 6 years, and we have owned a house together for the past 2. I would never cheat on him and wouldn't do anything he didn't feel comfortable with. My best friend is the person of interest and he is VERY respectful of my relationship with my boyfriend and would never do anything to compromise it. He is open to being my secondary, just only if my boyfriend allows it. I am always open with my boyfriend, he knows whenever I am hanging out with my friend and I would never lie about it because I see no reason to.
Also, I guess it wouldn't hurt to add. A few months ago, while all three of us were hanging out, we ended up having a threesome (my boyfriend is straight so he didn't do anything with my friend). It was great, but in the end it left me very confused. My boyfriend said he did it for me because he knew I really liked my friend. We have never done it again, even though I obviously would like to. When we all hang out my boyfriend sometimes makes jokes implying us doing stuff together, so it is just sending me mixed messages. It feels like he would only allow it on his terms and he wouldn't want us to have an actual relationship.
I have been very patient with my boyfriend, and I'm willing to wait for as long as it takes. I just am starting to lose hope.