What Causes Spotting And Lack Of Menstruation While Intermittently Smoking Marijuana?

I have missed two periods. My first was spotty and now this one is not even here. I take birth control and it comes in the same day and ends on the same day EVERY month. But for the past 2 months, I ve been smoking marijuana two or so times a week. And I haven t had sex. Could the marijuana be the cause of my period being late and not coming? Please help, my boyfriend is already mad at me.