Relationship Problem

I have been with my live-in boyfriend for five years now. The first two years was great. We had respect, kindness, love and trust for one another. The next three years we began losing it all. We love eachother, but I would say, we lost what we had, about seventy-five percent. We each have different issues with one another. My issues with him are: I sense that he lies to me about a variety of small things. But, a lie is a lie. Now I find my self not trusting him or not believing alot of things he tells me when I ask him a question about something. When he has a problem with me, he wont tell me. I can tell by his actions that there is something bothering hime and so I have to get it out of him. He says that I get mad when he tries to talk to me about it. Theres other things wrong with our relationship but it would take to long to explain. How can I trust him again? How can I get him to talk to me when somethings bothering him without me having to pry it out of him or guess what it is? I want us to be happy again. But I'm not even sure what he really wants. How do I start a conversation with him. to discuss how i'm feeling and whats really going on with him about if he still wants to make this work? Help! I feel so lost with him I don't know where to begin!