No period

Hey yall! So I am exclusively breast feeding.. I had my son in November. After I had my son I only bleed for about a week or two and then I stopped. Well I had started bleeding again around week 5 or 6 for about a week

At my 8 week check up I told my doctor and she said it was probably my period.. I then got on birth control pills. But since then I have not had a period. My question is..is this normal? I feel like I should probably be haven my period since I'm on the pill but I'm not sure since I'm a first time mommy and I'm exclusively breast feeding.. So is this normal? Should i call my doctor? My husband and I have only had sex like 4 or 5 times and we have used condoms for all but like 2 times.. I can't be pregnant can I?