Hi 13runette. I can relate completely to how you are feeling pregnancy-wise. I'm also 7 months pregnant with a two year old, and I feel very tired, first trimester was floored with sickness. It's hard and I nap/rest at lunch when I get the chance and get early nights. I'm usually asleep on OH on the sofa by 9.
What I can't relate to is the additional stress (and it sounds significant) that is being put on you at this time by your ex being so unsupportive. His behaviour is out of line - it's not OK and you should not have to tolerate this.
He should not be calling you lazy, for starters.
I'll tell you a bit about how things are our house, not to say this is right (and less so to be smug) but instead to give you a comparison, so that hopefully you can see that what he's telling you isn't right.
OH makes space on the sofa. He cooks more than me. We split cleaning and looking after toddler 50/50 but if I'm knackered that day he does more and I lie down (guilt-free). Weekends he takes toddler out for at least two hours, when I rest. All pregnancies are different. My last one was fine - I did everything normally - but it's not his business to distrust or challenge me. If I say I'm too tired - I am.
How was your partner in your first pregnancy? How is he feeling about this one and the new baby coming? How is your relationship in general?
I feel quite annoyed on your behalf. He needs to grow up and support you.