Right now you are living day to day, trying to survive this with some sense of sanity in tact.
You are in survival mode and that's a good thing...we all experience that.
Your #1 priority right now is you. You need to heal. You need to learn how to deal with this. You need to know how to move forward.
The reason for the sudden changes in emotions are because your world was turned upside down. Up is down, down is up and your trust in almost everything has been shattered. Shattered at the hands of someone you never thought was capable of hurting you so bad. This is very normal.
Your WH ought to be doing all he can to help with the healing and to prove to you that he is truly remorseful for the adultery and the pain that it has caused you.
Along with constant reassurance that he will never do this again!
It's going to take time and your WH needs to buckle up for the ride. There will be good days and awful days.
No matter how many roses he sends, no matter how many gifts, etc, your WH needs to keep doing this over and over to show you that you are the true love of his life and that he truly regrets what he has done to you.
Building trust should be one of his most important priorities. The only one to feel guilty, should be your spouse.
Look at the length of their affairs..how much time they spent cheating, putting themselves above you. Look at how they connived, manipulated, lied to do what they wanted to do. Now, there should be no limit on proving that they made a mistake, proving their own guilt in this and proving that they take full responsibility for what they've done.
There should be no limit on the time it takes for them to regain your trust.
On average they say 2-5 years to completely heal from an affair. You can't fast track it but it does get better. Allow yourself to feel everything you feel, good bad and otherwise.
If not, it will come back to haunt you down the road. Triggers are tricky like that.
Hang in there. We are all here rooting for you.
Hugs and prayers