I had breakthrough bleeding after missing a pill 2 weeks ago. now i should be on my period but i've only had cramps and a headache, but no blood. why?

Probably normal: Even missing one birth control pill may disrupt the delicate hormone balance that leads to normal cycles in women. This will usually clear by the next cycle or two, especially if birth control pills are resumed. Menstrual bleeding on birth control pills is drug induced and no period usually means there is no uterine lining tissue to discharge. This is a benefit to some women using bcp.