Late period, seriously fed up!

Brianna • 18 years old, partner 20 years olds, pregnant with our first..and second! And we're both over moon excited for our twins
16 days late and still getting negatives, I'm not ttc, I'm not stressed, haven't changed my diet, haven't done anything different, just want an answer. Do I keep testing or I've already got a negative so just let it go?