I am worried that if I tell the border guard I am visiting a fiance they may think I am trying to come down to get married and stay in the USA... but I do have a job here in Canada and besides my fiance is also Canadian and there on a student visa, but of course I won't be able to prove that at the border!
What can I do to make my border crossing smoother? Should I just say I am visiting my boyfriend, or a friend? Will they think it is wierd that I am driving? I don't want to fly with 3 cats, and I can't find anyone to take care of the cats for 2 months, and they go everywhere with me anyway, and I prefer driving

Is there any documentation besides my passport and birth certificate I should consider bringing?