Help please!

Hi everyone I'm freaking out! I gave birth on 12.02.15 my Baby will be 3 months on Wednesday. I breastfed for 5weeks right after birth and change to formula after those 5 weeks of exclusive bf. I still have not gotten my period! And I'm fraid i might be pregnant or that's normal for periods to take time after giving birth? Ok ready help me! Every little advice or anything will help. Thanks in advance!