Skipping my period??

I have missed my period for the month of february. This has happened to me before and I knew my time of the month was coming and i had my usual pms symptoms. A few days later I realized my symptoms had faded. I assumed I would just miss my period, which I did. Is this normal? I just started having sex with my boyfriend so I don't know if that has anything to do with it or not. I'm 120% sure I am not pregnant, only have had sex one time. It was brief, 1st time sex. He had on a condom and he did not cum. Help, I'm not sure if I should be concerned or not😰