Yo, you have no real proof whether or not he actually lied first of all. Second of all, you can't change what happened so either level with it or leave. I'm sure that later in your life (as well as his, when you two do break up because you are reading well too far into this) there will be situations that make the beginning of an exclusive relationship a little... gray area. You may be sorta seeing someone, your partner may be in a weird situation too. That's perfectly human, and kinda common in my experience. What's important is that you know about it, which you did, he literally told you and had avoided them it sounds like. Learn to be present with him and realize that the past has lead you to this present.