Paranoid. Please respond!!

Emma

So I had sex around MAY time and he wore a condom! Then I took my period twice ever since then, my second period then was around 11days late. I was suppose to be due my period on July 22nd but now I’m 18days late?! I’m absolutely freaking out, my my stomachs not bloated but I’ve serve back pains, and my stomach would have weird pains.. What’s wrong with me??