Filling A Gap
I'm looking for advice with my current relationship.
My boyfriend & I've been dating for about nine months, but before that we had been online friends for four years with a high degree of emotional bonding & kinky flirting. We talked for hours every day, shared everything, and had a lot of similar fantasies/complementary ideas about what we wanted in a relationship. When we finally ended up on the same side of the country and started dating, things didn't go as well as we thought they would. I was his first sexual partner and he had a lot of expectations which I didn't meet. Originally he broke up with me with the goal of dating more attractive people until he wanted to have a long-term relationship with me. We stayed FWBs, the sex has gotten better for him, and he's decided that he wants to keep his relationship with me while adding a second girl to fulfill his need for physical attraction. He has a theory that it's almost impossible to find someone who meets everything you want in a partner, and poly is an enjoyable way to get all of your needs fulfilled without causing resentment/divorce/etc. Since I'm bi, he theorizes that this arrangement will also let me get my queer fix.
I'm having a lot of trouble accepting this idea, and I still feel very unattractive. He's told me that I'm just not his physical type, he values the emotional/mental bond that we have (it goes well beyond friendship and deep into kinky territory), and he doesn't want to stop sleeping/cuddling/domming me, but he wouldn't be happy if he didn't get to fulfill his "shallow, immature" (his words) physical needs. Should I appreciate that I have a wonderful boyfriend who's willing to deal with all the hassles of trying to find a third person and values my personality and mentality, even if he also wants someone with a different appearance than me, or should I try and find a partner who finds me physically attractive? I feel shallow myself for considering throwing this all away just on the basis of physical attraction, since he has no problem sleeping with me/satisfying my kinky desires, but at the same time, I'm terribly insecure and I don't know if I want a long-term relationship where I'm constantly wishing my stomach was flatter/boobs perkier and wondering who my partner's really thinking of while sleeping with me.
Is polyamory a good way to obtain something that you can't get in your current relationship, if both partners are interested in it, or does trying to fill a gap with poly mean there's something fundamentally wrong with your relationship?