period after birth


Hello ladies, plz i need help. I gave birth on d 29th of March. Am EBF I had my period or what I thought was my period on d 27th April to 1st of May. since then I haven't had my period again. I have been having unprotected sex with my husband and have been feeling dizzy n other symptoms. but now am confused because have done so many test and they are all negative. have taken more than 7 tests. but there is no sign of my period. What should I do? or is it because am breastfeeding?