Bleeding a lot after sex

I had to get my period within two days and I ended up having sex for the first time. I started bleeding a lot. Flow was very heavy that I couldn't leave the bathroom 😭 I never planned this to happen and I fainted a lot during this process, for almost 6 to 7 hours and it started to come under control after my boyfriend got me a medicine from the pharmacy. Please help me, has anyone experienced this? Is this abnormal?

I'm very scared, I don't think I'll ever have sex again..