cheated on me :(

You will have to talk to him about this. But first, calm yourself down before addressing this. It is understandable (and perfectly normal) that you will be angry and upset but it is also important to be able to talk through the issue without being clouded by these emotions. It is important to have “the talk” because it will be on your mind even if you try to ignore it. Hence, it will be better to understand the context (i.e. what really happened) rather than having you imagine all sorts of scenarios based on what you saw on his phone. Stay calm (try!) during the talk. He may become defensive saying that you shouldn’t be checking his phone or he may be very apologetic and keeps apologizing. Regardless what his reaction is, try to address the main issue and keep your emotions in check. We tend to say things we don’t mean when being ruled by our emotions. Take a break from the talk if needed and resume when either/both parties have calmed down. Consider/anticipate your reactions as well. Right now, you are angry at what you have found out. You need to consider if you will forgive him or what can he do to earn your forgiveness. In other words, what can either party do to move past this incident? No marriage is perfect and what matters is how we handle each crisis. A couple can either fall apart or grow stronger depending on how things are being handled. Know yourself, understand what are within the limits that you can accept or how amends could be made to build trust. Communicate with each other so that things could get cleared up. All the best!