This will depend entirely on how much you want the relationship. Only you can answer that question honestly and you will probably need to spend some time thinking about it.

Trust will take time, especially if it was already lost once. There is no real way to make it magically come back, you will just have to build it over time, probably a lot of time. It will start with the little things, keeping small promises and the like and end up extending to the entire relationship.

It is a process, some counseling would probably help a great deal but that is all up to you guys.

If you decide that you do not want the relationship now then the best you can do is get out of it quickly and don't look back. Take the band-aid approach and get it over with. If you draw it out it will only make it a more difficult decision, stress you out even more and drag your mood, daily life and so on down with it.

Good luck to you.