The first thing I'd ask is if you are on any kind of hormonal birth control? I know that can interfere with your menstrual cycles and even cause a missed period when you are not pregnant. Stress or weight loss can also cause you to miss a period.
The second thing I would ask would be if you have had any pregnancy symptoms at all. Swollen/sore breasts, abdominal cramping, morning sickness (which doesn't have to be in the morning), frequent urination, mood swings, and heavy fatigue can all be signs of pregnancy. If you have had those symptoms, it's possible you are pregnant and the "period" you got was actually pregnancy spotting.
I'm actually not sure if a pregnancy test would still work if you would already be 2 months pregnant by now, but you could try, but if it is negative still see a doctor just in case?