You could be in this predicament. You have acknowledged that what has happened has happened. But the chance that your partner may stray again is preventing you from taking the next step. So what you really are trying to find is reassurance that it won't happen again. You want a 100% guarantee that your partner will stay faithful to you.
The first point you have to understand is that there is no way that you can be 100% sure that your spouse won't cheat again. Your spouse's behavior is something which you cannot control. To wish for something that cannot be, will only add to your suffering. This is something you have to acknowledge before you can move on. You have to recognize that your spouse may cheat again.
So, if you accept that as fact, how can you move forward? It is very important to appreciate that this is the chance you take in any relationship you enter. There will always be a chance of getting hurt when feelings are concerned. At this stage, what actually counts is how likely it is that your spouse will reoffend. The likelihood of your partner cheating again can be measured by observing 3 sets of behaviors.
1.Does your partner absolutely recognize what you have been and are going through? Do you sense that your partner really appreciates what he/she has done and what he/she has put you through. This is a extremely strong indicator of how committed your spouse is to saving your marriage.
2.Does your spouse take on complete liability for the affair? If the answer is "yes, they do," and it is unconditional then there is far less likelihood that they will re-offend.
3.Is your spouse committed to making the necessary changes? If you think that your partner is making a huge effort to making the changes to his/her behavior then you can feel much more secure in the knowledge that they probably will not cheat again.
If there is clear evidence that your spouse is meeting these three sets of criteria then you should feel much more reassured that they will not be unfaithful again. If there is unambiguous proof that your spouse is 100% committed to acknowledging the errors and making the essential improvements then you are in a much more secure place from which to offer forgiveness.