and that you are doing it to yourself.
So personally, I would try to identify where the guilt comes from because most people only feel guilty in relationships when they have done something wrong or kept pertinent information from the people they are friends with. Just off the top of my head I can't think of anything people do to themselves that they feel guilty about except for eating cake when they told themselves they should be dieting.
So long as you are openly and honestly discussing your feelings with them, and understand the difference between cowperson and poly lover, and if you can't be poly lover than cowperson isn't an option and you know how to be a caring friend, you have nothing to feel guilty about.
What you do have to be careful about, is being honest about whether or not you would be willing to be with her if she broke up with her boyfriend, because if that is the case, it takes a person who is has become so adept at practicing honesty it is like second nature. Because you will find yourself behaving in ways that you know
aren't conducive to healthy relationships (esp healthy poly relationships) and the person who does not understand that honesty is a practice won't recognize what they are doing, and so they will justify their actions which is more or less a conscious decision to be an asshole home wrecker.
But I did not get that impression of you, so please don't take my harsh tones personally, you come across as being very genuine and it sounds like you are trying to do the right thing.
Something that most people don't
realize is that there are many fine lines that drawer distinctions between different types of "poly people" and all the different ways to practice polyamory.
The problem you are having is not really that uncommon, it is just that most poly communities would automatically tear into you for being a mono and justify their actions under a banner of poly heroism. But the truth is most people, if not all, have an easier time sharing their more casual lovers than they do their more seriously involved lovers.
Not to make the assertion that polyamory includes casual relationships, but just to avoid the primary/secondary type talk that always begins the bickering that ruins every thread.
I know polyamory is focused on love, and I don't want to do the concept of LOVE a disservice and I don't want to paint you as being monogamous because many poly people subscribe to "the one" = "monogamous/cowperson" as I firmly believe that you can love and be in a relationship with many, but there are also those whom you feel so connected to that you want to share your life completely with, so in order to be polytically correct (which actually makes me sick to my stomach) I will say there is such a feeling as "the ones"
And from your words you know exactly what I mean by "the ones" or what monogamous people call "the one" and to be honest I see people who need to divide love into monogamy and poly as equally confused, so in full disclosure lets just say I am far more disgusted with the mentality of poly ID'd people as they are far more wrongfully discriminating than mono ID'd.
But anyway "the ones" which are sometimes referred to by life of a certain sect, as the figure eleven https://www.youtube.com/watch?v=n2JwBT_sX74
, and it just means that
overwhelming love can be for more than one other person, but still can and does feel like a curse before it can be recognized as a blessing.
Before I get off topic, I should point out what others have, and realize that her desire for children may not be compatible with you desire to not have children -- and I do not mean biologically -- as two women can get sperm from any idiot male. Families with Women as parents have children all the time.
Do you realize that if he husband wasn't in the picture, this overwhelming love for your lover could easily have you agreeing to be parents together?
Because you are attempting to practice poly you are presented with the opportunity to experience that overwhelming love without having to compromise your desire in life to not have children. Many people under the influence of overwhelming love end up compromising too much of their dreams in what they wanted out of life and find themselves ten years or twenty years down the road with their Love having gone sour, extremely bitter and hateful towards each other, often never realizing that is was compromising an aspect of their life they didn't know was not something they couldn't compromise on and remain happy.
You need to be very careful with this overwhelming Love because if it were a plant it would require lots and lots of nutrients to grow, but the fertilizer it requires is one specifically formulated for overwhelming love and you will kill it if you just get miracle grow (or any other more plausible sounding brand that doesn't say on the label "Formulated for overwhelming Love")
It's always good to know the direction you want to go in your life, and children are one of the major directions it's possible to orient your travel by walking (at least until you can fly) and whether or not you desire children is a difference like North and South in regards to the Four Quarters of Direction available
So perhaps you should realize that for this experience, practicing poly will enable both you and her to not compromise parts of your this life it wouldn't be wise to bend on, as it would sour your love.
If you only thought you didn't want children, all I can tell you is you sound like the type of person who understands, so as long as you all practice what you know must be practiced to have a healthy relationship, you will get over this painful part and it will be worth it.
But I know that doesn't bring any comfort when you already feel punched in the stomach. But if he is a respectable man, there are very minor things he can do that will alleviate some of the pain, but he will need to be aware of it. Which can be done so long as you all trust each other AND are trustworthy
I don't envy you, but you've found one of the ones, and it doesn't sound like all is lost, and part of the process of having All found
, starts with the pain you've described, if you are with the right people, stay the course, you will be glad you held fast, as when you reach your real limits relief will come quick.