I'm 17 Years Old, And Regularly Have Protected Sex With

I'm 17 years old, and regularly have protected sex with a condom with my boyfriend. I've had three negative pregnancy tests. My period is almost always irregular so I never for sure know when it should come. My cycle is on its seventh week so I've been worrying. I've stressed out a lot about this in the past few weeks to the point where I've made myself sick. Is there still a possibility that I'm pregnant after three negative pregnancy tests and having protected sex?