My boyfriend's cheating on me but he doesn't know i know...?

I've been with my boyfriend for over a year now. He moved in with me about 6 moths ago and tells me everyday that I'm the one who he wants to spend the rest of his life with and tells me that i'm the only one he loves. He went overseas just before he moved in with me and i know that he met someone over there. becasue of that, she has moved to this country for about 2 months now, i duno for how long, but i know she is here. There are so many clues and so much evidence that i have that all points to this fact, i am 100% sure that there is another women in his life. I dont' want to let go of him and the sadest thing is i still love him, and as far as i know that'll neva change. I want him to admit he's wrong, i want him to tell me the truth...i'm in so much pain, knowing that he's doing such a horrible thing behind my back and lying right to my face...i really don't know what to do...if i confront him, he'll just make up excuses, i've tried before. Someone please tell me what i can do