Pregnancy issues. Results came negative.

Hi. I'm 19 years old. I had unprotected sex on 28th aug, and after 3 days I did the pregnancy test. It came out invalid. Again the next day I took pregnancy test, or came out invalid. The next day I took an ipill. Following next day I took pregnancy test from different brand ie.prega news. The result was accurate and came out to be negative, before I had used ican. After taking ipill, I guess I've been experiencing some pregnancy symptoms MAYBE. The symptoms I've been experiencing are: Stomach cramps,Headache Fever ,Burps and unnecessarily farting I sleep more than usual ,Pee colour turns out to be more darker than usual,cough and cold ,Unusual feels in my breasts (sometimes) .As I'm not sure about my periods. My periods have never been regular as such. The last time I had my period was around or before 11th August. This month I don't know when I'll be getting my periods. Even after having all these symptoms I did a pregnancy test today, I used prega news and results came negative.