I hate using cliches but in this instance they are very apt - not least 'what's done is done'.
Sounds trite I know but it's the reality. You can't go back, you can't change anything, you can't undo it .. and by going over and over it you are perpetuating that cycle of guilt, shame, remorse, regret and grief. The only place this affair exists is in your mind and memory and to an unknown degree, in the minds of memories of those affected by it.
I hate to say this, but you are wallowing. That might sound harsh but the constant rethinking and analysing, picking over the bones of what is dead and done is stopping you from moving on.
You have to try and set aside your emotions and allow your logical thought processes to take over. And before you say 'I can't' let me assure you, you can. This is how all recovery works - the transition from emotional response to thought response. It's the whole premise on which CBT is based.
You made a horrible, horrible mistake. You cheated on your husband with another woman's husband. You got pregnant by him, were abandoned by him and had a traumatic abortion.
That's a lot of shit to contend with and of course you aren't going to be able to wave a magic wand and make out like it didn't happen. Of course there's going to be emotional fallout – you wouldn't be human if you didn't feel hurt, grief, anger, shame and all the rest of it. But you can't (and won't) go on feeling like that forever, so why prolong the agony?
Just for a moment, set your feelings aside and look at it logically. You did it. End of. No going back, no changing it. The guy you had the affair with turned out to be a prick. Nothing you can do about that either. That's his problem, his wife's problem, or his next lover's problem, it's not yours, so set it aside, better still discard it. Stop reliving your 'hurt' over how he treated you and start thinking in terms of how lucky you are to not be with someone like him.
Your husband still loves you and you love him. The affair has brought into sharp focus just how much you love him. You (and he from what you have told us) have come out the other side of this. You have. You are writing about your affair in the past tense. You are writing about your abortion, your confession ... all of it, in the past tense, because that's where it is. In the past. You are through it, it's done - what you are left with is the emotional aftermath. You now have to deal with those emotions otherwise you will never be able to give your loyal husband who you tell us 'adores the bones of you' the love and commitment he deserves.
Set a time limit on your grief. Allow yourself a day, weekend, week whatever ..... a period of time when you give yourself permission to 'wallow' for want of a better word to your heart's content. Revisit it if, relive it, go over it, allow the emotional response free rein, weep, wail, shout, scream, write about it, talk about it, whatever comes, let it come. Then set yourself a date/date from which you are going to stop wallowing and consciously make an effort to start moving forward.