To Early To Tell??

Niib

I haven't had my period since about the last week of September (honestly I don't remember having it in Oct.). I haven't had many symptoms. I think the main one I've had is the smell. Certain things really irritate my nose and makes me feel sick. I've taken two tests so far and both came out negative. Is it possible that I could be, but my hcG is low? How long should I wait to take another test? (if you haven't guessed I've never been pregnant before lol).

 I've been off BC since August (got period Aug and Sept), so is it possible that my cycle might have changed?

 Any help would be wonderful!