As long as the tests are showing negative and u did not have any further unprotected sex ,you should not worry for pregnancy,hope you have not taken any ipill as that further delays the periods and sometimes causes loads of harmonal imbalance especially if u have irregular periods issue, I suggest you should either get ur harmonals checked,like thyroid , betahcg,and also get an ultrasound done to see for PCOs which is primarily responsible for not only period delays but also hampers your fertlity. Should you need any further information or assistance you may get back to us.