Bleeding between Periods while on Birth Control (Pill)?

i just got off my period a week and a half ago and just today i started bleeding like if i were to get my period, but i'm on birth control & i sometimes take it at later time than usual because i simply forget & i've missed just two days during the 6 months i've been on the pill, should i be really concerned about the bleeding or is it normal due to the fact that i'm not taking my pills responsibly?