I was making love with my girlfriend on 20th November, she got her period on 28th November, I am scared that she might be pregnant

Hi Mgs,

If her period was "normal" for her then she is likely NOT pregnant.

Timing wise, it would also be UNLIKELY that she'd get pregnant.  You had sex about day 20 of her cycle.  She normally will ovulate sometime between days 11 and 16 of her cycle, day 1 is when her period starts.  The egg is only viable for about 48 hours - so it likely died at least two days before you had sex.

Hope it helps.