I don't get along with my boyfriends son, please help?!?!

I'm not looking for judgement, just help.. My boyfriend and I have been together for about 2years and have been living together for over a year, we get his son every other weekend, also everyday after school for a couple hours, I hate to say this but I hate the kid a lot, and sometimes I like him! We have great days and alot if horrible days,He's 7, parents have been divorced for over 2years now, and my boyfriend lets him do what ever he wants! He Swears more than a sailor! He says F*** constantly ( and every other cuss word you can think of) also he has hit me several times before, always saying hes joking, but i know hes not. i have to get after his dad if he does something wrong, because his dad will let him get away with murder! constantly flicks me off just for shits and giggles! He whines when he doesn't get a toy when were at he store, gets crazy when he can't get candy from the gas station , and if we're not doing what he wants to do he will whine till he gets a satisfied answer., the kid always tells me I'm not be boss of him, I understand I'm not his mom but when he does things he's not supposed to, and I ask him to please stop, he keeps doing it, he also tells me that it makes him happy when he pisses me off, just the other day we went out and seen an old friend of my boyfriends, my boyfriends friend was trying to say hey to his kid and he was just quiet, I said he's just a lil shy sometimes, the kid smiled and so did i, then said I'm gonna smash something in your face! This kind of stuff happens all the time when the kid meets new people, I'm just so overwhelmed, me and my bf fight a lot so it probably doesn't help, my bf fights infront of his son with me and that makes me mad more than ever because I know it isn't appropriate for that to go on, while the child's mother is in his ear saying things about me that a child shouldn't hear at his age, he's so spoiled, still sleeps in his dads bed so I sleep on the couch majority of the time, it ruins me and my bf relationship every day more and more! Please help!!!!