Similar position to Ledkr for me.
I forgave my STBXH for registering on Online hookup sites. 8 times. I forgave him because I believed what he said (only looking at pictures, didn't contact anyone). I forgave him when I found a letter he'd written to one of the contacts. Because he told me he had drafted it and not sent it.
Whether he had cheated or not, (and he still won't admit it, because then I'd be right iyswim) he definitely cast out a line into the water.
The whole time of forgiveness was sadly not one of forgetfulness. I found myself trapped in a life of doing things to make him stay. Looks, sex, not going out, being the cool wife.
It's not a life you can live sanely in for very long. Especially not a positive one in which to nurture your DC.
When he left I felt like a huge physical weight was lifted. I only had to trust myself. There's no feeling like it.
I look back now and barely recognise myself, the strong woman I was in my 20's that wouldn't take any shit. Reduced to an absolute mess.
I have a DP now and yes of course he could cheat. And so could I. Would I forgive again? I don't think I could live with that. And now I know that I can survive, it makes me feel stronger about facing that situation should it arise.