First off I am sorry you are here and that he has done this again to you.
Your first priority now needs to be you. Eat when you can; sleep when you can and keep those fluids up so you can think straight.
Did your WS put the work in after the last A's or did the A's get rugswept?
If he didn't do the work to find out why he keeps having A's then he won't have the tools to stop. Also, if you rugswept there were no consequences for him o, in his eyes, he probably doubts deep down that you will leave him.
Two things struck me about your post.
The first is that the OW brazenly was at your house and just so happens to get ill so she can sleep over?
I don't buy this- I think she (or they) planned it.
The second is the fact his second A carried on for 2 years after you found out. Did you know this or did he take it underground? If you knew but were hoping to wait it out then you have given him a message that there are no consequences which may be why A number 3 has come along.
BUT-BUT... these A's are NOT your fault.
You could have been a supermodel in looks but he still would have cheatedbecause the issue isn't to do with you or how you look or act. It isn't about what you did or didn't do.
It is about him having something broken inside of him- so it is his issue not yours.
My advice to you (if you want any decent shot at your M) would be to throw him out and initiate a 180 (look in the Healing Library for details)
Once you can see in his actions that he is remorseful then you can decide what you want to do.
My fear is that if you don't take a hard line straight away then the pain of this will just get prolonged for you.
You don't have to decide what to do immediately but you do need to decide that you are worth far more than being a wife who gets cheated on.
You are better than what he has offered you up to now. Trust me on this.