Are you with him only because you're lonely, afraid of hurting him, or out of habit? If you're still seeking other men/possibilities through dating apps/craiglist or constantly checking out other men, then the odds are that it's not working for you.

I had a similar experience. I met a guy, we hit it off, but once the initial infatuation and whatnot faded, I realized it just wasn't for me, and I wasn't romantically interested. I kept trying and going because he's a great guy and I didn't want to hurt him, but after 6 months together, it was tough. He realized something was off and we talked and decided it was best to break it off.

So, I guess you need to ask yourself if it's actually working for you. Relationships are two sided, so if you're not going to or struggling to commit 100% to him, then it's unfair for him. If you're still checking out other guys, or he feels like you're looking for other possibilities, he'll feel he's not good enough or being used, etc., and he doesn't deserve that; no one does. You'll be leading him on, and then the inevitable breakup will happen, and he'll be hurt even more.

If you break up, yes, he'll be hurt and yes, you'll feel guilty. There's no avoiding that. If you start "missing" him, and have thoughts about getting back together, make sure to ask yourself whether or not if you miss him specifically, or miss someone being there. IE: "I miss cuddling/holding someone before bed" vs "I miss cuddling with Go_Go_Fiasco's-Boyfriend-Here".

If you break up, don't try to be "friends" with him. That's his call, and his call alone. If he feels like he can continue as friends after time, then sure. If he'd rather erase you entirely (out of sight, out of mind) to heal, again, it's his call.

So, I guess the main thing you need to do is ask yourself, "Why am I still with X". If it's because you like/love him, great. You know what to do. If you are with him because of any other reason, then you're being selfish and you know what you should do and need to do.