You aren't, it's not possible to menstruate every week. If you're experiencing vaginal bleeding on a weekly basis then there is something wrong, you need to go see your doctor.
you could be pregnant.
why my period is come every week and 3to 4 days.
Normal !
Having your period means you did not conceive!
If you are still having a period, you are not pregnant.
Usually you get PMS symptoms about a week before your period is due to start.
NO.
Yes. You can get pregnant at any day during your cycle, including when you are on your period.
You're pregnant
If you took them every day for a week you would delay your period by one week.
Possibly, but you might be having your period. Go and see the doctor or midwife
every so often but at least once a week