Passing out on/before period

I’m 13 and started my period when I was 12. But in June I was at a zoo camp and passed out. They took me to first aid and the nurse asked if I was on my period. I said no cuz I wasn’t but 2 days later I got my period. Then last Wednesday I was at a water park with the fam and was in line and passed out! Then later that night I felt my period! My mom was talking to a friend and told her about it and said her daughter had the same thing. What helps??