Help..

I woke up feeling so nauseous when I was drinking my coffee in the morning all of a sudden I ran to the bathroom to throw up... I had back pain, bloated, and tender breast.. my aunt flow does come until October 21.. and I had sex two time this month on the 3rd and the 8th but on the 8th it was my highest fertile day which was at 33%.. when should I take a pregnancy test?