Pregnant and period

I had a period one month that was a bit off than my usual it lighter and shorter and came a lil late. Next month I had a regular period as normal . Next month I had no period and found out I was pregnant. Was I pregnant from the beginning or did I get pregnant at the last month ? When I got my scan at the doctor at the last month my baby wasn’t even a baby just a lil dot 🤷🏽‍♀️