I'm not going to say that he can be trusted or that this is a healthy relationship, but I do have to say it is NEVER okay to violate someone's privacy and read their text messages, emails, or other things. Not respecting someone's privacy is a boundary issue that you definitely need to work on. Even your partner has the right to talk to other people about things that he doesn't tell you. It doesn't mean the the things is doing is okay, but his wrong doesn't make your actions right! On the other hand he has demonstrated very poor communication skills. Dating someone else instead of talking to you about the problems in your relationship is not acceptable and is a form of emotional blackmail. It is just another way of saying if you did what he wanted you to do then he wouldn't have to cheat or be manipulative. In the same way his unfaithfulness doesn't make your snooping okay, your attitude or whatever it is he claims you are doing doesn't make his cheating and lies okay. It sounds to me like you both have issues that need to be addressed though not necessarily in a relationship with each other.