I've been here for almost 6 months now visiting my boyfriend, who is a citizen.
To continue to explore our relationship, can I cross the border as a us citizen and return a few days later?
Or is there a time limit on when I can return?
No - there's no official time limit regarding when you can return. But whether you are allowed back in or not and for how long depends on the opinion / mood of the immigration officer you encounter as you're reentering Canada. If the officer feels you've been spending too much time in Canada (effectively living here) or don't have sufficient ties to the US, there's always some chance you could be refused entry.
You would be far better off applying to extend your visit from within Canada rather than doing a border run. This is generally less risky.
Thanks for the answer.
Unfortunately there isn't enough time left now to apply for the extension, due to the cic website saying that there has to be a medical exam completed in order to apply for the extension.
