Well I think what this person did was not right. They lied and played on your feelings to feel bad for something that was not true. Seems like they were hiding something because if it was an innocent trip then they would have told you the truth. Also, if you found it by accident you was not checking up and you are not to feel bad for lacking trust because it is clear that they do not deserve trust. That is just their way of changing the situation and making you feel bad to take the attention off of what they did. I would say if you have not been together too long it is best to end it now. If you were married I would say try to get counseling and see if this marriage can be saved. But if it is indeed short term dating I think this is not a way to start a relationship. If this person is truly sorry they will prove that they wXXXXX XXXXXe and apologize admitting they were wrong and not trying to manipulate the situation. I hope this was helpful and I wish you the best of luck!