Heavy bleeding after sex

Husband and I just had sex. We are 18 weeks today and have only had sex twice during the pregnancy. It wasn’t painful but when we finished, I realized I was bleeding pretty heavy. It’s gone away now and only lasted during, but I was wondering if this has happened to anyone and if it’s “normal”. I have the at home Doppler and of course checked the heartbeat after and it’s still strong. Just panicking and don’t know if I should head to the ER.