Is it normal to bleed while on birth control?

So I had an abortion the 25 of February and started birth control two weeks after the abortion. I did bleed after the abortion and later stopped. However I have been on birth control going on two months and now I start the randomly bleed at the times I would usually have my period. I am not sure if my body is fighting to have a period or what. Since I am taking the birth control pills I am supposed to get a period when taking the ultimate blue pills. Last set of pills, while taking the blue ones I did not get a period. Can someone give me advice? Not sure if I should change birth controls or what?