My boyfriend and I have been together for 7 years, although we have known each other for 13 years. Three years into our relationship the concept of polyamory was brought up and discussed over a period of months. We did not come to any conclusions and since my boyfriend stopped bringing it up as a topic of conversation we stopped talking about it. (My boyfriend is the one who believes that he is polyamorous.)
A year and a half ago, he met someone online that interested him and he spoke with both her and her significant other about polyamory before he approached me. (According to him, he felt that since we had talked about polyamory previously he only needed to talk to me about finding a prospective partner.)
There were quite a few miscommunications on both of our parts. We're still trying to figure everything out. I'm still not comfortable with our situation and he's still wanting more than we've agreed on at this juncture.
To complicate things further, we are expecting our first child in October.
TLDR: I'm monogamous and my boyfriend believes he is polyamorous. He is currently involved in a restricted online LDR. Neither of us is happy with the situation.