Late period!!!! Please help ??!

I had sex 3-4 weeks ago w/ my boyfriend . We didn't use a condom but he used the pullout method. My period is now 2 days late and I'm worried. I took a pregnancy test and it came out negative and I have an 8 month old already , ( my boyfriend is not her father ) , so I know the pregnancy symptoms and I'm not getting any. What should I do ? Please help.