What Causes Nausea, Dizziness And Soreness Of Breasts?

Hi, my period was due on the 30th may 2010, 6 days earlier i noticed spotting but only when i wiped after going to the loo this lasted for 2 days and then i had what appeared to be a very light period for 2 and a half days which was only here and there and a lot lighter than my normal period and bright red in colour, i am unsure if this was implantation bleeding as i had symptoms of pregnancy (headaches,dizziness, tiredness, sore boobs, bloatedness, cramping, lower back ache and pains in my legs and had sex on 25/04/10 and 02/05/2010. my period is now, 6 days late and i have done 3 home pregnancy tests most of the symptoms have settled apart from back ache and cramping and swollen boobs, could i be pregnant ?