negative pregnancy test so i dont know what to think anymore

Ok i have been trying to concieve a baby for a while now , and when i get my periods i always get them and they are always on time or a day before or maybe a day after my expected day and they are always heavy so i kw its my period forshure. Anyways the last time i got my period was on Feb-2-12 my next period was due March-6-12 and me and my boyfriend have been having intercourse without protection alot , i am not sure if it was my period or what but on March-4-12 i got really light spotting and it lasted for a couple days but it was very light and faded that i only needed to use a panty liner. For about 2 wks now i have been having pregnancy sypmtoms or to me i think they are i have fatigue, back pain , cramping (although its not normal period cramping its more of very little cramps that last 2 seconds or so ) , when i stand sometimes i feel dizzy , i get extremley hot , and my nipples are verrryyy sore and hurt to touch and when i squeeze them both have a milky/clear discharge come out. I took a pregnancy test and it came up postivie then i took another it was negative and i recently went to the local planned parent hood and they took a urine test from me and said it was negative so i dont know what to think anymore ? Can anyone helpp ???