Hey, I Had My Period On The 11th Of Every

Hey, I had my period on the 11th of every month usually. On October 18th he came in me. I had my period in November but it started on the 7th & lasted 2 days. In December it started on the 9th. Now on December 17th, I am wiping an it is pink. In the toliet it looks like little tiny pieces of tissues. What could this be? Could I be pregnant?