How to prepare for a divorce?

Heads up, this is going to sound sneaky to some extent.

But hear me out.

I'm pretty certain that I want a divorce.

But my S/O doesn't know.

He knows I'm unhappy, depressed, etc, but it's been that way for so long that we've become complacent in it.

I have More than enough reason to want a divorce, but I'm terrified.

In the past 7 years I've barely worked( only night positions so I could watch our kids during the day).

I have no degree.

I spent all of my savings and earnings paying off his debts and securing our home.

I've funneled everything that I have and everything that I am into our relationship.

I've sacrificed all of my friends( his ex wife cheated, and I'm openly bi-sexual, so he was jealous of everyone who breathed near me).

I don't have close family( parents are deceased).

We have 5 kids together( my three and his two). I'm very close with his kids. One I've even raised since he was a baby and fought for in court.

Of all the reasons I have for leaving, our last babies were the tipping point.

He's always different when I'm pregnant( our biggest downfall).

He doesn't help with housework, the kids, or come to appointments.

He gets distant and degrading( as though I'm lazy or boring).

Which is not normally like him at all.

I was pregnant with twins.

He swore it would be different this time.

But his attitude changed after a month.

I told him for two weeks that I was in pain and exhausted and didn't feel right.

He wouldn't listen.

I told my OB. She didn't listen.

He made no accommodations for my pregnant body, because the OB said I was fine.

Finally it got so bad that I curled up in his office floor( WFM) and cried telling him how sickly I felt and how I hadn't been sick the whole pregnancy.

He didn't even look up from his phone( game), "Well, what? Do you want to go to the hospital?" before going on about missing work.

I never did make it to the hospital, but my baby stopped kicking a few hours later and was pronounced stillborn the next day.

The symptoms I was having were consistent to TTTS, and my baby could have been saved gad I had the energy or help to go to the ER.

Now our surviving baby is 5.5mo, and I just can't let it go.

I watched my mother die, and those were still the most painful months of my life- carrying my dead baby.

I can stay and accept that we will never have a rainbow baby and I will probably never sleep with him again.

I mean, he's wonderful in basically every other aspect aside from when I'm pregnant.

But then I'd hate myself for degrading myself and my baby.

Or I can leave with little or no help and three kids to care for.

Ugh.

*sorry for rant*

How do I even begin to pick myself up and move forward from here?

And is it wrong if I plan a divorce like a year in advance just because I know he will not do so willingly?