You've gotten some really good advice here abnheel.
Remember the hell you went through? She went through it too - and she may not even understand why.
3 weeks is a pretty finite period, abn. It takes time to regain and rebuild trust.
Not to scare you, but it took a good year for one of my exes to trust me again - and that was the one who forgave me.
I hope your relationship was more stable and it will be far quicker a process - but the point is we may not get to set the timer on how long all that may take.
Communicate as fully, honestly and openly as you can - but more than that - *show* her you're a changed man by what you do.
You'll get there
D