Well, that 's a very sensitive issue to talk about. Restoring trust after infidelity is like sailing a boat through storm in a sea. Communicate more and try to bring more transparency in your relationship. But do it only if your husband is found to be guilty of his actions else it is just a waste of time, you should then think to get separate.
This is a very painful and shocking discovery but in a way you may feel somehow “relieved” that it is finally out in the open now. If your husband is repentant and is asking you to forgive him then there may be a chance to start rebuilding trust again. If you can forgive him, that is the starting point, but he will need to earn your trust again, and that will take a long time. He needs to prove himself to you over a long period of time. You cannot do this alone. You will need help to have an accountability structure in place. If your husband is serious about regaining your trust he will be willing to go for marriage counseling or therapy together with you.
Trust may be gained with difficulty and lost easily. Once lost, trust can be difficult to restore. Before asking how to trust again, perhaps you should ask yourself whether you should. Trust is not something to be given away freely; it must be earned. If your husband broke your trust, you must determine whether you think it’s likely to happen again. If so, trusting him would be folly. If you understand the factors that caused him to stray and you’re confident he won’t cheat again, then trusting him will be easy. Most people fall somewhere in the middle and must rebuild trust in small increments over time.
If your husband appears remorseful, and seriously sorry for his actions, then that is a start. Take it that the marriage is still important to him and that despite his mistakes, he is willing to make it up to you for the affair. A trick I read somewhere is to set ground rules for your husband, which he will have to strictly follow. This allows him to take the first steps to be forgiven in a way that you feel is fair.
Men cheat because they are not happy in their marriage, or they just seek some thrills. It is up to your ownself to decide whether and how you can forgive your husband for his act. To help you gain trust in your husband once more, you must make sure that your husband is sincere about making it up to you for his mistake. Get the help of a professional counsellor if you feel at a crossroads.