From January 6th count 14 days. That is approximately when you would have been ovulating, give or take a few days. BUT if you are trying to determine who the father is, this method does not work since sperm can live inside you for up to 5 days in ideal conditions.

so say i had sex on the 18 and then again on the 24th..thats too close to tell

Yes, that is too close to tell. Because they could overlap. You'll need a DNA test when the baby is born.