Advise?

So me and my partner have had unprotected sex since 2nd of December, I cannot track my ovulation or periods in any way due to previous forms of contreception that I have been on, but for the past 2 weeks or so I've been feeling nauseous constantly, tired and on Tuesday I began having brown spotting and well I've done a pregnancy test and it's negative but is it too early? Could I be pregnant? Any advise appreciated!