Am I just tripping...?

So I had sex December 4th. We used a condom and he pulled, pulled condom off, and "came" on my thigh. However, it was my first time having sex in 9 years. My period came on the 10th like usual and went off on the 14th. However on last Wednesday I was spotting and cramping like my period was coming back. Only happened for that day. I hope I'm not pregnant? No way right? Is my body going through hormonal changes??