First of all - congratulations on your custody battle.
Secondly - I understand how hard it is to not only try to support a partner through breakup grievance; but to also have a partner who shuts you out
in some large way during their process: be that hiding away, or not wanting to hear about your successes.
Am I right in remembering from an earlier post that D and C were together for 10 years??
If so, that is a very, very long time indeed and I can understand why he is still depressed after two weeks. Not only does he have to unpick a decade of habit and connection with this person... he also has to let go of any codependent guilt he may be feeling (or even pure, normal, "I dumped someone vulnerable" guilt).
Most importantly, he's getting help from someone else. We all (myself included) can be guilty at times of expecting our partner to be our sole source of comfort and congratulations. It's natural to feel that way - especially if you feel you would offer both in return.
I do not think you are being 'me me me'. I think you are saying 'that is him' and 'this is me, over here'. You are saying 'where is the partnership here?'
Though I have never been diagnosed, I am pretty sure I've had some bouts of depression. Sometimes 48-hour black, morbid moods; sometimes week-long dark moments; sometimes longer. I've been through breakups. I've never been in a headspace where I haven't wanted to hear about my partner's joy... unless, perhaps, that joy relates to another relationship... then it just feels like rubbing salt in an open wound.
However, I haven't ended a 10 year relationship, either. I think it might take him a very long time indeed to get over this.
If this helps at all... I have been in your position with my girlfriend very recently (and once before). She broke up with her secondary of 2 years, whom she loves with all of her heart and soul. She was devastated; completely wrecked. She and I usually talk for hours and hours every day, about everything under the sun. When this happened, she completely pushed me away. For the first few days, her mind needed to lash out, so she blamed me for their breakup, because our relationship had been growing closer and she'd been giving him less attention. She was battling grief, guilt, anger, sadness; everything really. For an entire month, she barely spoke to me at all. She would go for days on end not speaking a word, just hiding away and not coming out for 48 hours. I was starting to wonder if I would ever see a glimpse of the girlfriend I knew again. In the end, when she finally came out into the light, our relationship was even better than before, because she was amazed at how I'd been there for her for this whole month with nothing back.
Giving support can be the most strenuous of all when one of two things are happening. When you are either the sole source of support and the depression is relentless - or when you are being completely shut out.
I understand you feeling down because he's not 'present' in your relationship right now. I personally think that's natural and normal. If he broke his bones and was in hospital for an extended period of time, you'd feel lonely and strange without him there. You would be focused on supporting him through his injury; but of course it's ok to feel sad, too.
I do think that it's perfectly reasonable for you wanting to share your news - I cannot put myself in his headspace, because even when I'm completely depressed, there's still this tiny light in me that doesn't want to shut my partner out.
Poly breakups can be tricky and awkward for the other partner too (i.e. you). If you didn't have a high opinion of the ex, it's hard to keep hearing about her and find that place of altruistic support. If you thought of lot of an ex partner, it can be hard on the metamour because the metamour might be losing a friendship or positive influence too; then it's hard to find constant support when you are grieving yourself.
The bottom line is that I do sympathise with you. I would say give it more time. You might have a long road ahead of you, but you should get closer and closer to the light. Be patient - and when you don't feel patient, don't express it. I find it horrendously painful when my GF tells me to snap out of it after a week or two of blueness or depression. You can't just snap out of it. He's getting professional help and that is good.
One last thought is that I noticed he does what my GF does. He raises a topic, then doesn't want to hear you talk about it and doesn't want to talk about it more. Ask him what he needs. It sounds like he actually just needs someone to listen without interacting - a sounding board. Does he need cuddles, space, to offload, to feel understood, to have a conversation, to talk about other stuff? If you find out, you may feel more productive offering it. This way, you can achieve some sort of feeling of interaction in the relationship - even if what he needs is 'space'. (The act of 'giving' space is 'giving' something - and it can make you feel less lost and worthless in the situation).
Finally, can you do things to alleviate your own stress and blueness? Do things with your children, take them out? Any friends? Start a new hobby or invest in a current one? Any other partners you can turn to and enjoy time with?
My GF and I use an analogy of a cup for these things. Sometimes, when you've given and given and you're starting to feel overwhelmed, stressed or down yourself... think of it like a glass full of water. It depletes the more you give to someone else. When it's hitting the bottom, you need to do something to refill it, so that you can healthily manage to keep on giving, whilst looking after yourself. Anything that replenishes feelings of joy in your life would be good for 'refilling your cup'.
Me: (30f) open poly
GF: (40f) My long-term, long-distance partner
Hubby (37m): GF's husband
Garcon (26m): GF's submissive/third partner
“Peace comes from within. Do not seek it without." ~ Buddha