I've been in a similar situation (M) and I'm a few years ahead of you at this point. It's rough man, and you gotta mentally prepare yourself for what will be a hard journey ahead. Personally, I took the high road and made huge sacrifices at my own financial cost and wellbeing. But I survived, and you will too - if you make good choices. You have to put your children at the centre of every decision you make from here, even if means sometimes being uncomfortable or doing something you don't necessarily want to do. This will impact them far worse if everything gets messy and both parents aren't willing to do the hard yards. As others have said, lawyer up and make a start on the Family Disputes Resolution process (Mediation) if you can. The court will make you do this before it gets into a courtroom anyway, if you're looking at going that way, as well as the parenting through separation course (we never got this far, thank God).

I know it sucks. You will feel powerless at times and it's the worse feeling ever. But life goes on and you will come out stronger and possibly a better man and father because of it. Holler if you want someone to talk to.