I had sex 7 days in a row my period was due the 21st and it came three days early which would be the 18 could i be pregnant?

Probably not: If the bleeding was your period, then you are not pregnant. You can have bleeding in early pregnancy. If you dont want to get pregnant, i recommend using condoms until you can see a doctor to discuss other birth control choices. If you are trying to get pregnant, start taking prenatal vitamins and make sure you are not any meds that are dangerous for pregnancy.