I am current 15. I am 4 days late on my period, but my period has changed over the last year from the begging of the month to the middle then to the end. About 3 weeks ago was the last time me and my boyfriend has sex. EVERYTIME we did we used a condom and pulled out, after we finished we did the water test and none of them had breakage. My boobs are sore like they normally are before my period, but like I said I'm 4 days late. I don't know if this could be due to stress because I have been stressed this whole month. I also did a pregnancy test 2 days ago and it was negative. Should I worry ?