"I may have mentioned it, but in moments of agitation, he's told me this would all be fine if I just found someone else. This not only annoys me, as I have no intention of taking more time away from my children to go on a boyfriend hunt to make this relationship more comfortable for the current boyfriend...but it's making me feel like a failure. He tells me how his wife is so swamped with pms on their kinkster site she has to turn her pms off to get away from all the men pursuing her. I don't have that problem. (Of course, I'm not on any kinkster site, but neither do I have this problem at OKCupid.) I've been on two dating sites briefly with no great romance (I should add I was on them only half-heartedly, because I'm not dying to have a boyfriend.) He tells me how he used to try to pick up women in stores, and a relationship site tells me the grocery store is a great place to meet men--nobody has ever tried picking me up at a grocery store! These are things I wouldn't even be thinking about if he hadn't said these things, but now a small part of me wonders what's wrong with me and when BF will start to wonder why no one else is snatching me up."
I'm just going to throw this out there, and I'm sorry if it's hurtful or unhelpful:
I'm not too impressed with the sound of your boyfriend, WhatHappened. I don't think the problem is that you're a secondary girlfriend--I think the problem is that he's not being as helpful to your life as you are trying to convince yourself he's being.
I don't think he's a bad guy at all. I just think your relationship with him may have served its purpose--it helped you for a time and made you happy for a time--and now it's time to go your own way (and eventually find someone better).
I'm speaking as a person who is happy in the kind of "partial" relationship you describe. I'm in a similar situation--very full life with my own stuff, plus a great guy who takes me out for dinner, drinks, hot sex, etc, and who has really helped me emotionally and makes me happy, but it won't ever be more. But I, personally, don't WANT more with him.
If you DO want more--then I think you must leave him.
Related to that, but more so: I detect a hint of a manipulative personality streak in your BF. I think that's why he's drawn to single women while claiming he wants a partnered woman.
I dislike the way he is being insensitive to your lack of interest in--and to your lack of time for--seeking another partner. How would bragging about his wife's kinky pms help you? How does it help you to hear how great he is at picking up women in stores?
(I certainly will never want to hit on anyone, or be hit on by anyone, in a grocery store. Grocery shopping is an annoying chore and I prefer to get in and out as quickly as I can. People in grocery stores are distracted and frustrated and not dressed spiffy).
I don't like that he's conveying to you a sense that he would be your primary if only he didn't already have a primary. To me, that's not what poly is about. (I can't articulate what it IS about at the moment, but it's NOT about finding someone who would be your primary "if only").
I wonder if his insistence on his deep, deep love for you is a wee bit manipulative?
It's perfectly reasonably to break up with someone because you don't feel satisfied emotionally or don't feel like it's going anywhere. Doesn't matter if they're poly or whatever.
Single, straight, female, solo, non-monogamous.