Help I can't be pregnant??

So I had protected sex a month and a half ago and not had any since. I had my period about two weeks after right on time. It seemed normal, a bit shorter than normal but otherwise nothing alarming. I was due yesterday for my period and I have all the symptoms like pressure/cramping but no actual flow. I've read some things about implantation bleeding and now I'm psyching myself out thinking it was a lighter period last time and I could be pregnant. Should I be worried?