I've had my share of friends with benefits, or FWBs, over the years. It's nice to have someone who you're sexually compatible with and actually like, for the occasional play time. It sure beats having to look for hookups, if you're the sort who does that sort of thing. I am that sort, but I'm also lazy, and sometimes I just want a bit of a deeper connection with my sex partner than what can be found with an attractive stranger.
I have had a few different types of "benefriends." I've had the sort who are basically just regular, repeat hookups. We get along okay, but we aren't likely to just hang out, or anything. We don't have a lot in common, but we're attracted to each other and are sexually compatible. I've also had benefriends who were actually friends that I'd hang out with, but we'd also have some hot sexy times on occasion. This meant that, unlike with that previous type of guy, not every single time that we were together ended up with some form of penetration. Then I have also had what amounts to an intimate friendship. We lay on the bed, watch some movies, make out, get naked, cuddle, and do some form of foreplay, but keep it pretty tame, and that's about it. All of these arrangements have their merits.
The risk in an FWB situation is in catching The Feels for that person. The delicate balance in having a friend with benefits is that you want to compartmentalize the sexual aspect of the relationship, without allowing it to evolve into romantic feelings. You still need to have some sort of feelings for this person, otherwise they'd just be a hookup. If you lose the sexual attraction somewhere down the line you're just gonna end up as friends. Which is fine. But if you can't manage that compartmentalization you risk unrequited love. And the chances of it being unrequited are likely pretty high, I imagine. You never know, though, you might both be into one another.
So, what do you do if you catch The Feels for your benebuddy? I'd say that honesty is the best policy. Yes, this may destroy your relationship, but that might be for the best. You may still be able to get it to work, but it's going to depend on how well the two of you handle this revelation.
If you tell your pal that you think you're falling in love, they may panic and send you packing. They may feel awkward and not know what to say to you. They may stop returning your calls and texts. They may scream, "Oh, my God, me too!" Be prepared for any of these responses. I honestly don't know if there's an easy way to reveal this to your fuck buddy. I mean, it would likely depend on the person. With one person, you might be able to blurt it out, shrug it off, and resume fucking. With someone else you might have to put it delicately and beat around the bush. Fuck if I know. I think the only thing I do know is that you wouldn't want to do it while you're in the middle of fucking.
I've developed feelings for buddies before. They weren't strong feelings, I guess, but there was some speculation on my part about what would happen if he and I started dating. But before I even got a chance to confess my feelings, he was mentioning how he's not the dating type or something to that effect. I took that as a hint. Maybe he suspected something was up and decided to make a preemptive strike. In any case, we managed to remain friends. At some point, though, we did stop fucking, but we do still have a rather intimate relationship. We know dirty little secrets about each other, and that works for us. We still get along great and enjoy each other's company, but I don't penetrate him anymore.
I guess you have to decide if you develop feelings for this person and they don't reciprocate, do you really want to torture yourself by fucking around with them, and maybe making out, and doing other things that couples do, without being a couple? Can you handle that? And, can you handle that without passive-aggressively taking it out on your buddy or resenting them?
What if your pal develops feelings for you? Do you want to have that in the back of your mind while they're staring you in the eye and their naughty bits are interacting with your naughty bits? If you can handle that, more power to you. If not, then I guess it's time to part ways.
I would really, really suggest that if you do end things with your FWB, that you do so directly. Don't just stop talking to them, or ignore their calls and texts. This person wasn't just a hookup. They were a bit more than that and they deserve the courtesy of a pseudo-break-up. They at least need to be given a reason why you're not going to meet up with them anymore. It can be as simple as saying that the change in feelings just complicates matters too much and you think it's time to move on. Whatever you do, though, don't just leave them hanging.