took a test already and was neg, what should i do?

Ok heres the thing my period started on 5/3/12 had unprotected sex with bf round the 4th, 9th, n 16 very spreaded out. I have a 24day cycle and my mens only last For about 4days. Then had very light bleeding which started on the 17th and ended on the 21st which was two week b4 my period was due. The last time this happen where my period came on two wks after it had just went off i fount out that i was a mth n a half pergnant with my now two yr old son and was wondering if this id the same case thats going on now and how long should i wait to do a pregnancy test being that my period wasn't due to start til the 27th of this mth took a test already n was neg what should i do?