I'm 22, Pregnancy or PMS? I have irregular period

So, I'm 22 years old student, and I'm really worried I may be pregnant. I have irregular periods, and usually very bad cramps as well. My period started on 12 of March last time and I had unprotected sex during the whole month. But my boyfriend ejaculated inside of me only twice (It was somewhere between 5th and 10th April for the first time and 12th April for the second time) the other time there was no ejaculation inside. I'm still scared I may be pregnant, cause my period is now 11 days late. I have very typical PMS cramps since 10 of April and really terrible Acne break out on my neck and my face for the last three days. I don't have any other symptoms like nausea etc, but I'm extremely tired, a bit moody and sleepy all the time. I still hope It may be just stress, I was abroad and got back one week ago, what was very difficult for me emotionally). And I'm also very stressed about the fact that I may be pregnant.does somebody have the same experience with Acne and cramps? Could early pregnancy look like PMS? Could actually huge stress cause late periods and tiredness?  I would be glad to hear anything about it!