U can have sex, but it is possible (not guaranteed) that some leftover blood from ur period will come down. If u don’t want to risk it, then it’s best to wait at least a few days after ur period.

You can cause yourself to begin bleeding if you have sex after your period. Think of it as ripping a scab off a scrape. It will bleed. Wait about two days post period to have sex. The brown discharge is just old blood/spotting. Count that as a period day of light spotting.