Hi, I am in need of an opinion and or advice. In the moment on May 30th I had unprotected sex with my boyfriend. We were careful as you can be and he did not ejaculate in me. But not too much longer after we had sex unprotected again, we were aware of the dangers and checked it out to make sure there was no left over ejaculations on him. He said everything was fine after checking. He did not ejaculate again, but there was some pre-ejaculation but not inside of me. He is sure of this, and i believe him for he is aware what is what. But I always think of the what if's. My last period was May 4, I have been on a regular cycle of 28 days for 3 years now. I am only one day late, but it worries me because I am always right on time. I know the chances of being pregnant are very slim, but I cant help but worry. Not only that but I have been emotionally stressing a lot the past couple of weeks and get weird stomach clenches from stress. The people I have talked to say I am late is just because im stressed. I have been told to go to a doctor for possible stomach ulcers. But never have. I know I am stressing a lot but how can I be sure that is why I am late? I am almost 18, I realize I am still young and periods tend to change at a young age. I don't know if i believe this is the case, if it is then it is terrible timing. Should I be worried? The main concern, how unlikely it is or not is pregnancy. Also the fact that im off track and I have never been off. What should I do? Should I be worried?