What Causes Spotting, Bloating And Nausea?

i am married and me and my husband do not use any contraceptives, but he 'pulls out'.
i have not had a period for going on my third month, which is hard to believe because usually i have long heavy periods which last about 7 days,
;last month i had brown discharge for 3 days and then it subsided at about the same time i was due for my period,
and now i am tired blotted and nauseas(not vomiting though)
i took 2 pregnancy test and both were negative.