Pregnant?

So 18 days late and still no period. I took tests at my 10 day mark and 14 day mark but all negative. Let me add that I am on birth control, the Nuva ring to be exact. Me and my boyfriend have sex pretty much everyday, without protection. I was a week late taking the ring out last Month but I put in the new one 7 days after like I was supposed to. Not sure if I should bother taking another test... maybe it's just a side effect from the birth control and not pregnancy?