Started my period 4 days early was heavy & mild cramping 4 2 days now it's light brown could it be implantation bleeding had sex the week of ovulation?

Pregnancy test?: It's always a good idea to take a pregnancy test if you have had unprotected sex and your period isn't normal. If the test is negative (and if your last unprotected sex was more than 14 days ago), then you can feel safe. Sometimes periods are irregular for no good reason. Sometimes it's stress, illness, travel, or weight changes. If it only happens occasionally, then i wouldn't worry.