So - clearly this was significant enough that I have been examining myself, the situation and my responses to it. I genuinely care for this person, and know he does for me as well. I wish him no ill intente, and, indeed all the best!
I am considering all your input and my responses - though I think overall the "ambiguity" of the situation is what bothered me most. I do not easily fall in love - nor do I historically tend to feel insecure. When I like someone I know it fully. And - though that is the case with this person - the surrounding situation gave me much caution and anxiety.
I think part of it was his response to my query regarding why he had not ended things with his partner. Had he said: "Because I love him fully and have no reason to end things at this time." it would have made me feel like: OK - this is a man that knows where he's at and is solid on his loving foundations.
However - it was a bit emotionally vague to me: "it would crush him" does not sound so much like a loving answer as a 'I'm in control' answer. I don't feel my partner has enough fortitude to weather the impact of a separation. True or not, this is giving him a position of power and dominion. Does not feel realistic or compassionate to me.
Also - (I know this was brief on specifics) - the night I had my anxiety attack it was precipitated by the STRONGEST POT BROWNIE I had ever had - on low blood sugar and a very emotional week. All contributors, I'm sure - but at the time I was somewhat obsessed about whether or not this person might leave me if I did something "wrong". A fear of my own, I admit.
With regard to whether or not I might feel this anxiety in any new relationship situation based on my usual make-up or particular to this affair, I STRONGLY feel it was situation based. I am not a child - I've had a number of short and long-term relationships... I know how I tend to react and respond emotionally when I am in a 'mono' relationship and I feel secure. This was all new territory for me - and us in general.
I think there were a number of factors here that contributed to my anxiety and reactions.
Firstly, as this was the first time I'd felt such strong emotions after my last breakup, I think I got into this a bit too quickly. I think I should have continued dating others as I got to know him better - not feeling so totally vested in his time and gauging how much he really wanted to be with me - and to some degree what lengths he would go to to insure securing our bond.
Two: I met his partner too soon. I think I needed to feel more secure with him and OUR relationship before I confronted the reality of his partner. I was in no denial over their relationship, but honestly feel I needed to feel more stable in what WE actually had.
Three: I gave up too much of my time and power to be with him. I habitually changed my schedule/plans to accommodate him - and rarely felt he did that for me. That set up a 'lop-sided' emotional scenario in my head, and I should know better by now. I should not "over-accommodate" just because I "want to see someone" or especially because I am "feeling insecure". It's silly. We all have busy lives - if they are interested they will willingly wait.
Four: On more than one occasion - in a half-hearted effort to protect my own emotions or confusions surrounding them, I made excuses for not responding sooner to his overtures or queries - when I really should have honestly said: "Hey - this is going a bit fast for me - I need some time on my own to think things through. I have no other interests beside you, but need some time to think and adjust". He saw right through my excuses and I think it made him anxious/annoyed. He was nothing but honest and VERY direct with me. I tried to be - but was not as direct as I should have been. Sometimes I am not as direct as I'd like in an effort to either spare someone's feelings, or "stall" whilst I think things through.
And, though I have no problem with his partner, the idea of sharing someone is a very new/foreign thing for me. Though I generally don't consider myself terribly demanding, I am a one-person person. I'm sure going slower with all of this would have allowed me more time to figure things out and not get overly emotional/overwhelmed too quickly.
One last caveat: He does NOT like to be touched - AT ALL - while he sleeps. And though I don't need to be all over/wrapped up with someone all night, it makes me feel FAR more emotionally secure when I am touching and/or held even if peripherally than not touched at all - which makes me feel un-liked and vulnerable. Minor?? Maybe. But then again, maybe not.
Responses? I hope so. Can I salvage/resolve this at this point: probably not. I think my apprehensions gave him too much pause to go forward emotionally with me.
But only time will tell - as it always does...