I personally am not a big fan of Fallout Boy... but I have listened to them to attempt to broaden my horizons on newer music... The song makes perfect sense to me... I interpret it as a guy that gets "played" by a girl.. hence "i'm just a notch in your bed post, but you're just a line in a song". He catches her sleeping with another guy "don't worry i'm watching you two from the closet, wishing to be the friction in your jeans" which I think is a cool line... and hence they're "going down, down, in an earlier round, sugar we're goin down swingin". The only thing that doesn't make sense to me is the controversy around whether he says "loaded god complex" or "loaded gun complex" right before he says "**** it and pull it"... It would make sense that he says "loaded gun complex" because he says "i'll be your number one with a bullet.../loaded gun complex\... **** it and pull it" but people still insist he says "loaded god complex".