accuracy on PT after 4-5 weeks after sex?

so in the month of June, I had unprotected sex 3 times. each time, the guy pulled out & finished on my stomach. the first & second time we had sex was about 5-6 weeks ago & the last time was 4 weeks ago. I am on the pill but I like to take tests just in case. I've taken 5 so far & they've all come out negative. do you think it's safe to say that I'm not pregnant? thanks!