Sex in a car

Caroline
Didn't see my partner for almost two weeks as we both had work in different places, we decided to make it our mission to see each other as we missed each other , we decided to go to the cinema and I told him I wanted sex afterwards so we decided to go to a forest on our way home and had sex in the car for the first time 😁😁 we always wanted to do it in the car but I was afraid as I never had the experience before doing here lol... It was the best 😁😁 after having sex I started to bleed a small bit and by the time we got home there was loads, stopped this morning tho. What could be the cause of this ?