Hi op, I've been in your position.
It takes a huge amount of time of energy, of love, of commitment (non to mention money) to bring a child into the world and raise him/her into adulthood. I think as women we know when we can't give it our all... It's bigger than the fear of giving birth or of sleepless nights... It's visceral.
For me, I knew in my heart of hearts that I couldn't give this baby what it deserved, and I didn't want to put my children, my marriage and my mental health at risk. I decided I'd rather regret an abortion than a baby.
You have a family, you are a mother. It is completely natural imo to put your existing children's needs - and your own- first. It's not selfishness, it's not brutal... It's a form of love, in a way. It's life
Which isn't to say that deciding to terminate a pregnancy is easy - quite the opposite. But someone on here gave me excellent advice when I was u your position... You need to separate the process from the outcome. You need to come to a decision, gain comfort it's one you can live with -knowing that sadly there's no right or wrong... And then see it through.
You are a good person, a good mother. Be kind to yourself, seek counselling if available, talk to your dh. You will know what to do, and you will be fine.
Thinking of you