I've been trying to think of any feedback to offer, and I really don't have much. This is a tough situation.
1) My only experience with "lesbian bed death" comes from a Queer as Folk episode where the lesbian couple revamped their sex life by having a hot threesome with an ex. I guess that won't work here
More seriously, I do have experience with (hetero) sexual activity declining as the relationship progressed. It turned out to be a sign that there were serious problems between us (or rather, problems for him that he wouldn't tell me about). I had no idea at the time, and kept trying to do things to vamp up our sex life--the last resort of which was for us to try seeing other people to gain more experience. (Worked for me, didn't work for him, but again, he didn't tell me what was bothering him. The end result was the worst break-up I have ever gone through. The post-end result was my realization that we had never been sexually compatible to begin with).
That's just my experience. I'm not sure what would apply here, except maybe the lesson that problems with sexual connection have deeper roots and are much harder to solve than one would think.
2) Alex's history of sexual trauma is a BIG issue, I think. Any reason why you didn't mention it sooner? It seems like an important factor from her point of view.
She can't meet all your sexual needs because of her triggers, so she gave you permission to seek sexual fulfillment elsewhere. But since then she's had to struggle with knowing you must have better sex with people other than her. I can see how hard that must be.
On the other hand: is she actively getting treatment for her trauma? Has she made any progress? What is the extent of her trauma--long-term childhood abuse, an isolated incident in adulthood, etc? It matters.
It does sound like it's remarkably easy to trigger her. All you have to do is drink a glass of wine and act like a normal, amorous partner? And that's too aggressive for her?
I don't have personal experience with sexual abuse/trauma. But I do know how YOU feel--guilty for the way you express sexual feelings, rejected every time you touch her too "aggressively," and FRUSTRATED.
Also, it seems to me like Alex must have been at least partly drawn to you because of you being sexually aggressive--I mean it seems like she must be a little attracted to that. Or else why would she be with you? Is there any way for her to make progress in therapy with the end result of becoming more comfortable with more passionate sex?
(My college boyfriend would flinch away and accuse me of being too "aggressive" if I merely put my tongue in his mouth. He claimed to have experienced a traumatic childhood, but wouldn't talk about it or seek treatment. I would be more sympathetic to him if he had not been an emotionally abuse liar. It took me years to become comfortable with my own sexuality because I felt like such a pervert when I was with him).
And, I'm a little confused by something you mentioned earlier about you being the one with a dysfunctional history, which made you feel like the "damaged" one while Alex was the stable one. (Yes? Am I remembering that right?) So you felt guilty for being poly because you feared maybe you were just dysfunctional with relationships?
But how does that fit with Alex being the one with a history of sexual trauma? Isn't she the one with more emotional issues in that sense? I guess I'm assuming the trauma is from her childhood; maybe it's not.
I don't know what to say, except that it must be really painful for Alex to know she can't fulfill you sexually because of something that already deeply impacted her life in a horrible way.
3) Ah. She's heavy. Honestly, I could guess that from reading between the lines.
I dated an overweight man once. I was WILDLY attracted to him despite the weight. But yeah, what you can do in bed is really limited. And he was really insecure about his body. So I hear you.
A lot of sexual abuse survivors become overweight as a subconscious way to hide themselves and their bodies. Did that happen here? Again, is she pursuing treatment for the trauma?
So Alex probably hates her body, feels physically unwell a lot because of her weight, and has to accept the fact that you have fantastic sex with other, much thinner women? That's a lot to deal with.
(And I don't think you "incidentally" chose physically fit women for your new partners. Nothing wrong with it, but there it is.)
4) Neediness. Yeah, this is where I really sympathize with you. I am also turned off by neediness.
Possibly, however, I might be turned off by normal emotions that I interpret as neediness, when in fact I'm the one with the problem. I haven't figured that out yet.
Is Alex excessively needy, or are her feelings normal but YOU have a hard time with feelings?
She does sound needy in an unhealthy way, but I can also see how someone in her position would feel that way.
I totally understand how sex can be WAY more fun when there aren't desperate & deep feelings involved. It's such a relief to be able to focus on the physical, to feel friendship & affection for a partner without the feeling that you and you alone are responsible for their happiness.
I don't have any good advice here. Except this: it is a BIG problem that you are flinching away from her, not wanting to make out, etc.
I think this goes back to your original question, the reason you started this thread. You wanted to know if it was okay to be so subsumed in NRE that you were losing interest in your primary partner.
I think the answer is no. Polyamory is supposed to be about knowing that having feelings for someone else does NOT diminish your feelings for your other partner(s).
I mean, I think it's okay to get caught up in NRE for a little while. But then it should blossom into a renewal of feelings for your primary.
When I sought (and found) better sex with men other than my boyfriend, my feelings for my boyfriend skyrocketed. Both emotionally (because he gave me permission to date others) and physically (because the good sex I was having with others gave me FANTASTIC ideas for things I wanted to try with him).
And the good sex, as well as the different type of emotions I had with others, took the pressure off my boyfriend to meet all my needs. Being with him was no longer frustrating because I could appreciate him more, instead of longing for things he wasn't comfortable doing with me.
As a caveat, the situation totally did not work for my (ex) boyfriend, so I can't claim that my perspective is a success story. But I think it would have worked if he'd been genuinely poly.
So I feel like that's what's missing in your story here: the feeling that seeing others should be HELPING your relationship with Alex.
I mean, I think you are progressing toward that point, but are not there yet.