I can't believe I'm about to say this, because I usually come on these threads to put the straight partner's perspective because posters are applauding the OP's authenticity.
I don't disagree with most of the comments here (your DH is probably having a really miserable time), but I think people are being quite harsh in how they're expressing them.
I've been on the other side of this. My XH ended our marriage to come out as gay. He'd first said he was bi, and just wanted to acknowledge that and work on our marriage. The bi period lasted less than a year. Then he said he was gay (and then denied he'd said that).
We'd been together 18 years and married 13 when he first said he thought he might be bi but it wouldn't change anything. Although I wanted to believe him, I couldn't escape the nagging feeling that it spelled doom for us. Why wait 18 years to tell me?
I've spoken to a lot of other people who have been through this as the straight partner, and most of us do start off trying to be supportive. In fact, I worked much harder than XH at trying to find ways to acknowledge his bisexuality that felt safe for our marriage. However, often, being supportive of the LGBTQ person means that the focus is much more on them. When I stopped to think about my experience of the relationship - lack of affection, lots of criticism - I started to realise that XH had never loved me the way I loved him. I now think he was always critical because he was trying to persuade himself that my faults were the reason he didn't feel attracted to me (nothing to do with him, not his fault, my fault our marriage wasn't amazing).
When I talk to other straight partners, it's not our partners being bi/gay/trans that upsets us the most, it's the lies, deceit and lack of respect and consideration as the truth comes out (they've been thinking about it for ages but it's a shock to us, they've been watching porn or had an affair, they start dating really quickly, start going out to gay clubs to 'find' themselves and leave us keeping family life going). The support tends to fade due to other behaviours.
It's been seven years now since my marriage ended. XH never apologised to me for the hurt he caused or acknowledged that his sexuality was the reason our marriage ended. He maintained right the way through his bi "phase" until we agreed to separate (in relationship counselling) that his sexuality was a distraction. He said that I was the only woman he could ever be with, but he couldn't be with me anymore because I was such a difficult person. I still feel angry about this at times - if there were issues between us,why not work through them? We couldn't! Because no amount of working on faults on either side could change the fact he's gay! I think it was cowardly of him not to just own that.
OP, if you've said anything to suggest that you're gay rather than bi, your DH has probably skipped the "we can make this work" stage and gone straight to "that explains a lot, our marriage is over". He probably feels stupid, unattractive, probably wonders if he is attractive to women or if there's something about him that isn't attractive to straight women. He probably wonders if you only married him because you needed a sperm donor. If you are going to take his children away. And so on.
I would also like to say that, in my experience, children cope much better if they're told an age appropriate version of the truth. It took my XH two years to tell both DC. They found it much easier to understand and accept our separation once they knew (both still in primary school at the time, now mid teens). Neither of them had any difficulty accepting his sexuality or his boyfriend and DC2 is a fierce LGBTQ ally and goes to their school's LGBTQ society meetings.