Brown discharge instead of a period?

Hey all. So I stopped birth control mid Dec as we are planning to get pregnant later this year. I know it takes some time for the hormones to work their way out of you and I've been on birth control for 13yrs. For the last maybe 3 wks I've been having brown discharge. I was supposed to have my period in the middle of those weeks but no actual blood came. Could this be just my body figuring itself out or should I be concerned that we have a surprise pregnancy?