If your periods started before you had sex, the chances of you being pregnant is extremely rare, less than 0.5% o 0%. The ovum (egg) has been expelled from the fallopian tube (the place where it fertilises) and hence can't implant itself.
- If you had sex on day 1 of your period (after it already started) than chances are you're not pregnant.
- If you had sex before you started your period, chances are that you aren't either as periods can't occur if conception occurs (eggs fertilised)
My words are
medical opinion, don't take it as
medical advice. If you want to be entirely sure, go for a pregnancy test after 3 weeks, but
personally I think the chances of pregnancy is very slim.
