First Time Sex - Bleeding

My boyfriend and I had sex for the first time yesterday. I am a 16 year old girl WHO HAS NOT YET HAD HER PERIOD.

I started bleeding during intercourse quite a bit, and today I am still bleeding substantially.

I have a question: Could the sex have triggered my period? Is that even possible? If not, why am I still bleeding and is that normal?

I'm beginning to get anxious and would appreciate feedback. Thanks...