How to break his heart?

So, lets lay some context. I am 30, male, and in my first relationship. My BF and I have been dating for 4 years this month. We currently live together with our 3 cats.Recently, my BF went on a backpacking trip. He wanted to complete his life's goal of backpacking the Pacific Crest Trail. I fully supported him in this, and took care of things at home while he was gone. It's a 6 month journey that he started with his best friend.The first week after he left, it was a bit awkward to have the apartment to myself, but that's it. I wasn't depressed, sad, mopey, or anything. I just thought, "it hasn't hit me yet that he'll be gone for so long." Well, it never did. In fact, he returned halfway through to take a month break. I thought I'd be excited for him to be home, but... I was annoyed. I didn't understand it. I'm a very cuddly person, and was especially before he left. Now that was all gone. I found I had become more comfortable with him gone, then with him at home.I think this is because I've come to realize just how vastly different we are. He is an avid outdoors person, I'd rather stay inside and play video games. He's not a gamer, AT ALL. I like anime, he doesn't. He's vegan, I'm not. We've always have few connecting interests, and I think his trip made me realize that, I'm not who I want to be with him around. I try to be who he wants me to be. I still care for him very much, but I think its best that we seperate.We are in a lease, but have a two bedroom, until July. My thing is though, I don't want to hurt him, but I know this will devistate him. If anything, his trip had the opposite effect on him, and made him realize how much he cares for me. He's commented before that, this relationship is different then his past relationships. So I can't bring myself to talk to him. I'm becoming more distant, and it's killing me. I know the longer I wait, the more distant I'll get, and it will just hurt us both more. I was determined to do it today, but when he got back from being out with friends, I couldn't do it.I know this is long, and I'm sorry. As I said before, this has been my first long term relationship, and I just don't know how to end it. Especially since it's holiday season, and we just officially hit 4 years. Anyone have any recommendations?