Why do I get brown discharge with some bloods in it during my midcycle to the next cycle?

When my midcycle starts, there is always a long brown discharge that lasts until my next cycle. We haven't had sex since September 4 (had unprotected sex that day outside ovulation window bc it was 4 days before period), and I got my period for September, October, and November

Is there a possibility for cryptic pregnancy / ectopic? I'm being paranoid, pls help