You want to be able to prove that your connections to the U.S. are stronger than your connections to your boyfriend. Obviously, that is probably hard to do since you are probably quite attached to your boyfriend, too, but they expect that. Any responsibilities or obligations back in the U.S. would be useful, like if you have classes to attend or jury duty to report for or anything that you're expected back for. This is to make sure that you will not overstay.
The main reason they are asking about a job is that they want to make sure you are not tempted to work illegally in Canada to support yourself while you are here. If you can show that you have money in the bank and even that your boyfriend and his parents have agreed to let you stay in their house, provide meals, etc., will help.
If you get an especially sympathetic secondary inspection agent, they might issue you a "Visitor Record" that you need to turn in a certain amount of time after you enter Canada. The only thing is that this is usually stapled into your passport, so I'm not sure it works with a card. Also, if they have a paper passport, they could stamp it with a short expiry date, but I think the card defaults to 6 months automatically.
Essentially, (as long as you're not a criminal or a danger to the public) they need to know where you're going, what you'll be doing there, that you will be able to pay your expenses without working during your visit, and that you will definitely return to the U.S. when the visit is over.
I would definitely try again tomorrow, but make sure you've gathered whatever evidence you can get to satisfy what I wrote in the last paragraph.