I think I'm just stressing

My boyfriend didn't finish inside me or come anywhere near it but I am nervous. Although I had two negative pregnancy tests 6 days after we had sex I am still worried. My period is 3 days late, but is has sometimes been irregular. I am feeling all of my period symptoms but should I confuse them with pregnancy symptoms? I don't have morning sickness or spotting. I am only 16 and I have been stressing a lot. Could that delay my period?