don't worry, it'll only make it harder, lol. relax. it's easier than it looks.
i haven't done it many times but the first time it happened kinda took me by surprise. i was riding one guy and another came behind me and just pressed himself in. there was a bit of pressure at first then he just slid in. it's definitely a WOWZER moment and my reaction was to try and pull away before they 'convinced' me to ride it out.
it feels good, but not in a "wow i just gotta have two cocks in me!" kind of way. i can't imagine women actually think that other than in a wild fantasy. i think that only happens in porn. in real life it's just something really kinky that you feel like doing from time to time when you feel like going wild and uninhibited. or something guys talk us into.
the right rhythmic movement on the right cock is still way more pleasurable than two of them awkwardly jabbing away at your sensitive lady parts.