I feel like he's living a double life?

I can completely relate to what you're going through. You need to talk to him and explain to him how you feel. Tell him that you want to be with him and love the way he is with you, but he needs to be honest if you too are going to continue your relationship. He has to grow up sometime, it may take leaving him for a short time to get it through his head, but if you really explain that you are about to leave him over this, it may help him to get it together a bit quicker. I did this with my boyfriend & had to leave him a few times for him actually to understand how serious I was, but he finally figured it out and he's changing into a much more balanced person now. Good luck, hope I could help.