The most f’ked up story ever

So I have 2 children, fiancé has 2 children and I’m now 10 weeks pregnant. SO is the provider for me and the children and has recently been diagnosed with multiple sclerosis. Although he’s in early stages and is on a progressive treatment he’s not the same. He’s refusing to get the proper sleep he needs over video games, he has mood swings which I don’t know if it’s related to my pregnancy or his sickness. when he does sleep it’s during the time I need help with our 1 year old the most. I’m so depressed, how am I supposed to take care of 3 children like this. It’s not a question about keeping my child. And I’m fully capable of supporting my children. Im just so depressed right now picturing having to do this on my own while watching my future husband deteriorate in front of me. I know pregnancy hormones have a lot to do with this but I’m having a terrible day. Is anyone going through something similar?