Its hard Karen. I think you really have no choice but to do some serious soul searching, but you seriously remind me a lot of myself which is why I have become some worried about this. If your FI is willing to do whatever you may possibly require of him to fix this I think the right thing to do is to forgive and work through it.
One day you will need forgiveness from him...it is just inevitable.
My FI and i have been through a lot in our 3 years and I know that because of our really difficult times we will have a lasting marriage...
Keep me posted on how you are doing. Your FI must be emotionally exhausted and I would imagine you would be even more so. Try to do something that you enjoy to take your mind off of things..a nice massage or something? Just a thought!