I had sex without a condom I have had to keep pushing my <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">period calendar</a> back and still has not started it was suppose to start the 26th and now it's the 28th. We didn't use protection but on the 27th I took a pregnancy test and it was negative should I wait the whole 14 days after sex and take another test?