Am I pregnant?

I had sex with my boyfriend on the 22nd of December. He is infertile due to Vericocele and did not ejaculate inside of me. However, we were not using any method of birth control. About a week later I started having cramps and breast tenderness. A few days ago, I started spotting. Am I pregnant? If not, what could other explanations for the spotting be? Is it too early to take a test?