Period end?

My periods are usually 4 days long. My last one I noticed blood when I wiped (brown in color, hardly any and not every time I wiped) the next 2 days after I thought my period was over. I didn't chart those days as my period but should I have? When does your period end exactly? When there is NOOOOO blood at all for an entire day OR when it's no longer dropping out on its own. I'm planning on TTC in July so I'm really trying to figure out my fertile days. I have been tracking my bbt but it'll go up for two days, drop one day. Then go back up. So I'm not super relying on it.