Omg I think I screwed up help

Ok so I had my period the 15 trough the 19 I was using a different <a href="">period app</a> and just discovered this one today my other <a href="">period app</a> said I was fertil the 18th through the 23rd we'll me and my boyfriend had sex this morning and he used the pull out method when I downloaded this app it says I'm 33 percent fertil is there a big chance I'm pregnant now