Well, I’ve been pregnant 4 times, including one very complicated pregnancy, so I do know how it feels. Yes, you can be tired and irritable/emotional at later stages but it’s not an excuse to be unpleasant or behave however you want. Yes, it happens, none of us are perfect and we all make mistakes (as did your DH by not letting you know he was going to be longer than planned)- that is not the issue here. What is the issue is just that you were being unreasonable- we all do it, apologise and move on- the issue is trying to pretend that it’s fine because you are pregnant and for that reason he should just accept unreasonable behaviour.
From what you said in your post it wasn’t just not saying “hi” when he came in, you said you ignored him and carried on with what you were doing, then went to bed. It sounded like you were deliberately giving him the silent treatment as a way to communicate your anger. Which is manipulative and passive aggressive, regardless of being heavily pregnant or feeling unwell. It is unreasonable. If that is not the case, and all you did was not say hello and then carried on normally, then I apologise but it is not what you had suggested in your post.
I hate it when women use hormones/pregnancy as a free pass for whatever they’ve done. It might be the reason for you doing something and perhaps can be a mitigating factor, but it isn’t an excuse and it doesn’t make it ok- nor does it mean that others need to accept it without complaint.
As I said, if my DH had been giving me the silent treatment, I think I’d leave them to it and would not check on them, whether he was unwell or not. Partly because they are being passive aggressive, which I don’t have any time for, and partly because I would assume that they wanted some space and to be left alone. Perhaps he thought the same, when what I think you really wanted was to be fussed over a bit because you aren’t feeling well. Which is fine, but I can see why he would have left you to it. This has then annoyed you further, because you perceive it as lack of care, so you send an angry text, which he has ignored. As would I.
He hasn’t really done anything wrong- other than running late and not letting you know (which is annoying but not terrible behaviour)- he just hasn’t read your mind and worked out what you wanted. He has probably done what he thought best by giving you space, given you had suggested that is what you wanted by ignoring him. I understand that you wanted him to check on you/make a fuss, but I think you are unreasonable to be annoyed that he didn’t, in these circumstances. You were not feeling well, which you told him, and then went to bed. You asked him to get a bag ready (which presumably he did? If not, fair enough to be annoyed at that). If you needed something, he probably assumed you’d ask- which you were capable of because you did. Perhaps he thought you wanted to be left alone, or were asleep?