We are all women here so I don't need negative comments under this post. I just need help & advice....

So August 13th I had unprotected sex & he ejaculated inside of me. The next morning I was due for my period but It didn't come until later that day & was light . I'm usually a heavy bleeder. I've been cramping since the first day but I usually only cramp for a day but it's more of a pressure type of cramp on my left side. My period lasts 3 days and today is the last day and it's still light.. My next period isn't until September 11th... is it possible I still could be pregnant? Do I wait until my next period ? Help please