Hi Doc,I Menstrated Twice Last Month Though The Second One

Hi doc,I menstrated twice last month though the second one I think is the fact dat I took postinor2 but after then have had sex with my hubby nd after the last bleeding it like 20days now nd still have not seen my period also have been having cramps nd tender nipples also I used atest trip to check if am pregnant nd the result was negative,wat can I do am so worried am not seeing my period.