Oh help. ** Stupid Question Alert **

[NotClever]

On Sunday, DP and I had unprotected sex. On Tuesday I started my period, very heavy as usual. How likely is it that I could be pregnant?
I know that I should know about cycles and fertility and ovulation, etc. but I don't

chances are slim to none

extremely unlikely.

To the point of being just about impossible. If your period came after the sex, then the period has wiped the slate clean and you're good for another month...

Crikey, that was quick!

Oh phew!!! Thank you lovely MNers for putting my mind at rest!