could i have got pregnant 4 days before my period

me and my husband had sex on may 5 and may 7 and he cam inside me both times well on may 9th i started my period but it was lighter and lasted 4 days and at the end of it was like brown so i had a blood test done on the 16 and it was negative but i think it was to early and this Thursday i started feeling a little sick but didn't puke Friday and Saturday i had some slight tummy pains with the sick feeling but no puking and i was really tired along with dizziness and today my lower back hurts but my question is could i have got pregnant 4 days before my period still have that period and not have my next one? which should be here around june 3rd and when can i test at home