[sc_rufctr]

^^^ All good but if you do get a lawyer don't "scream it from the roof tops".

That alone may be threatening to her. Certainly engage one to start putting your affairs in order but try to keep it discreet & nonthreatening.
At some point she'll find out but hopeful enough time has passed so that she doesn't panic.

This is important. Your lawyer works for you. Make sure they understand that and listen to them but think before you act.
No one know your ex better than you.

And YES start documenting everything. Buy yourself a small note book and start writing things down.
Just keep it simple. Date, time and what was said/agreed to.