<human>: Can you condense the text into three sentences or less?

So not sure how I should feel about this. My boyfriend and I have a great sex life. We are always experimenting with each other, and very open about everything. Tonight he told me he could never just have sex with ONE woman for the rest of his life. I can sort of understand this, trying to get in the guy-mentality... but what I don't understand is if this is a clue that he's been wanting to cheat, and this might be his way of getting "permission" and getting away with it. 

Now, my boyfriend and I have always been faithful to each other. I know he has fantasies about threesomes, and he says its NOT because he's unsatisfied with me, but I can't help but think there is something wrong with me to him?
Am I just unsexy after 4 years? Is there any chance he is using me to have a threesome? Just him bringing it up has brought up so many questions. 

Naturally, I came to Reddit haha. I'm not opposed to the idea, but he wouldn't really give me a clear answer on how much he would want this to occur, so does that mean he just wants another woman? Instead of an experience together?? He did say that he would only have love for me and we would be committed as we have been, but that he definitely wants it to happen more than just once. Lastly, if I do go through with this... I'm a total noob and have no idea how to even go about a threesome. Any advice on any of this would be greatly appreciated.
<bot>: boyfriend of 4 years says can't have sex with just one woman the rest of his life, but wants to be committed to me. what to do?