What really struck me about this article is that you asked yourself, "Am I forcing myself to change who I fundamentally am because of this social arrangement?" And for you, the answer was obviously "yes." However, I love this question because for some people, the answer would be "no"! So many times sexual monogamy is made to be a boogey-man for relationship woes, when in reality the problem is a particular person's incompatibility with monogamy as a relationship-style.
Sexual monogamy is great for some, and not for others. I'm interested in hearing more about whether you both plan to be socially monogamous as well (i.e. only have a serious emotional relationship with each other).